D i believe is the answer
ANSWER(S):
B. asserted
EXPLANATION(S):
A. murmured: too subtle
B. asserted: adequate
C. commented: too monotonous
D. snarled: too aggressive
1: Reading because it helps you remember the key subjects as in nouns adjectives and more. Also because when you see a more complicated word you can always look around the word to see what it means and use it in your studies!
2. To concentrate on what your English teacher is saying so you will get better grades.
B, because propel is to move forward.