Complex sentence: However, the a in car does not have its regular "short" sound (/ æ/as in cat) because it is controlled by the r. The r changes the sound of the vowel that precedes it.
Split into simpler sentences: However, the "a" in "car" does not have its regular "short" sound (/ æ/as in "cat") because it is controlled by the "r". The "r" changes the sound of the vowel that precedes it.