A. A has both genders of the students and since we don’t know the amount of students of either gender, this serves as an indication that not all the students are of one gender or another.
Answer A makes sense for me
the other sentence is B therefore
because therefore means so
my teacher was very ill therefore (so) a substitute was called to finish the day
The answer is C. He is an efficient leader who prompts his crew to work quickly .
A simile. A simile compares two things using the words as, like, etc.
