can and could are modal auxiliary verbs. be able to is NOT an auxiliary verb (it uses the verb be as a main verb). We include be able to here for convenience.
Can, Could and To Be Able To Exercise.pdf
We use I (positive) and couldn't (negative) for general ability in the past. But when we talk about one special occasion in the past, we use be able to (positive) and couldn't (negative). Look at these examples:
Although we look at be able to here, it is not a modal verb. It is simply the verb be plus an adjective (able) followed by the infinitive. We look at be able to here because we sometimes use it instead of can and could.
We use be able to to express ability. "Able" is an adjective meaning: having the power, skill or means to do something. If we say "I am able to swim", it is like saying "I can swim". We sometimes use be able to instead of "can" or "could" for ability. Be able to is possible in all tenses - but "can" is possible only in the present and "could" is possible only in the past for ability. In addition, "can" and "could" have no infinitive form. So we use be able to when we want to use other tenses or the infinitive. Look at these examples:
Many people find that they achieve the most success when exercising with a partner. Depending on the stage of the disease, it may be best for people with PD to train in an environment where others who could offer help are available if needed.
Pregnancy results in anatomic and physiologic changes that should be considered when prescribing exercise. The most distinct changes during pregnancy are weight gain and a shift in the point of gravity that results in progressive lordosis. These changes lead to an increase in the forces across joints and the spine during weight-bearing exercise. As a result, more than 60% of all pregnant women experience low back pain 13. Strengthening abdominal and back muscles could minimize this risk. Blood volume, heart rate, stroke volume, and cardiac output normally increase during pregnancy, and systemic vascular resistance decreases Table 1. These hemodynamic changes establish the circulatory reserve necessary to sustain the pregnant woman and fetus at rest and during exercise. Maintaining a supine position during exercise after 20 weeks of gestation may result in decreased venous return due to aortocaval compression from the gravid uterus, leading to hypotension, and this hemodynamic change should be considered when prescribing exercise modifications in pregnancy 14 15 16.
In this lesson, students learn the difference between could, was/were able to, and managed to. Do the warm-up activity with your students and then have them complete the practice activity and conversation questions.
Answer: Just like an independent variable, a dependent variable is exactly what it sounds like. It is something that depends on other factors. For example, a test score could be a dependent variable because it could change depending on several factors such as how much you studied, how much sleep you got the night before you took the test, or even how hungry you were when you took it. Usually when you are looking for a relationship between two things you are trying to find out what makes the dependent variable change the way it does.
The speaker wasn't able to attend the conference due to illness.She couldn't watch the match because she was working.They worked on it for months but they didn't manage to find a solution.
I could/was able to go there without an invitation. Is any of them (could and was able) possible here? The meaning is that I had an opportunity to go there without invitation. So, it's neither about a person's ability nor successful or not successful finished action. Has it to be just "I had an opportunity to go there?"
This lesson is helpful.But in questions ,Can we use could and was/were able to interchangeably?Like 1.Were you able to describe the person to the police ?If we use could here does the meaning still the same ?Plus we also use could instead of can to make it less direct .So is there any possibility if i use could here,it will refer to can,I mean a present situation rather than a past situation ?
No, they aren't interchangeable. "Could" indicates a general ability, and "be able to" indicates an ability on a particular occasion. So, "Were you able to describe the person to the police?" is correct because this refers to one particular occasion, not a general ability to describe people. "Could" is not right, for that reason. (Note though that the negative form "couldn't" may be used for particular occasions, unlike the positive form "could".) 2ff7e9595c
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