100 pointsread the paragraph below about breathing while swimming.

make sure to exhale all air underwater before rotating to take a breath. some new swimmers attempt to both exhale and inhale as they roll to the side for air. there is not enough time for both. exhaling should only be into the water and will take the form of bubbles. at first the timing may seem awkward, but with practice most swimmers will get used to it. check also to make sure you are not sinking down as you breathe. make sure you are rolling to the side, and not rotating your head and staring straight up. attempt bilateral breathing only after mastering the techniques above on one side.

what sentence should be elaborated on with further detail--so that readers understand the point of the sentence?

a. make sure you are rolling to the side, and not rotating your head and staring straight up.

b. some new swimmers attempt to both exhale and inhale as they roll to the side for air.

c. make sure to exhale all air underwater before rotating to take a breath.

d. attempt bilateral breathing only after mastering the techniques above on one side.