A. Los aerobicos
The question in English is "The best sport to strengthen the muscles of the shoulders is"
So aerobics is probably your best bet because the other options are yoga, swimming, and the last one I think is athleticism (Not entirely sure)
Because I do not know the context of what is "cool," I am going to assume that is referring to the weather/temperature.
In Spanish, we use the verb "hacer" in expressions that refer to weather conditions.
The direct translation of "It is cool," is:
Hace fresco.
We use the third singular form of the verb hacer because we are talking about the weather.
