The first answer should be correct, as none of the others make any sense.
As Mother drove, Father studied the road map. (B)
In this case, we just add the suffix. When we add the suffix to the words ending with consonant, nothing changes. For example, sad + <em>ness </em>= sadness or sad +<em>ly </em>= sadly. When we add the suffix to the words ending with vowel, again there is no change, because the suffix begins with a consonant. For example, state + <em>ment </em>= statement or force + <em>ful </em>= forceful.
