Answer:
a is probably what you are intended to answer, but don't be surprised if the answer is something else.
Step-by-step explanation:
I hate to start off by being a little cranky, but when you list a question with choices, it would be easy on the eyes if you made each choice into a new paragraph.
I don't know what the best answer is.
a) is certainly true, but it is the best answer. Maybe the new word is no clearer.
b) This is never true. Good writing never makes the writing unclear.
c) This is sometimes done, but not always.
d) This item is true, but self evident. The answer is between a,b and d
I think d is the most practical.
I think a is what you are intended to answer.