Find the synonym of the underlined word:
Her swollen tonsils are obstructing the doctor’s view of her throat.
 

The meaning of obstructing is obstructing a gap of a path or road. and that we must find the right answer from the choices given whose meaning is that the same as obstructing.
Option A) Encouraging - is an incorrect answer because the meaning of encouraging is ‘giving someone support or confidence’ and this can be not a synonym of obstructing. Thus, this can be an incorrect answer because the meaning of the words ‘encouraging ‘and ‘obstructing‘ doesn't match.
Option B) Assisting - is an incorrect answer because the meaning of assisting is ‘helping someone’ and this can be not a synonym of obstructing. Thus, this can be an incorrect answer because the meaning of the words ‘assisting’ and ‘obstructing ‘ doesn't match.
Option C) Aiding - is an incorrect answer because the meaning of aiding is ‘helping someone or giving support’ and this is often not a synonym of obstructing (but aiding and assisting is that the synonym of every other). Thus, this is often an incorrect answer because the meaning of the words ‘aiding’ and ‘obstructing ‘ doesn't match.
Option D) Impeding - is that the correct answer because the meaning of impeding is ‘delay or prevent by obstructing them’ and this is often the synonym of obstructing because they both have the identical meaning. Thus, this is often the right answer.