In the following questions, choose the correct word that completes the corresponding space in the paragraph below.

Doctors, writers, and many famous people have been diagnosed with dyslexia. __1__ (These/These people) and about one-tenth of the population experience difficulty in learning to read. __2__ (This/This difficulty) can cause both reading and writing to be a traumatic embarrassment for them. Neither intelligence nor educational opportunities seem to be the cause. __3__ (This/This cause) is still under investigation.