Answer:
a. Rods are about 1000 times more sensitive than cones.
Explanation:
The answer choice shown is a direct copy of the first line of the problem statement. It doesn't appear to be any more complicated than that. (It's a reading comprehension question.)
One major obstacle to developing good human relations is that man is fearful by nature. There are risks involved in developing human relations, and humans are mostly too scared to take those risks. Majority of humans are comfortable with staying in their own comfort zones, and would like to avoid the hassle of getting to know others.
They would have disliked that they had to relearn how to measure.