place particular or special emphasis?

Hi everyone,

I have a test in one of the textbooks. Before giving tests to my students, I always do them myself. So in a sentence

He placed .................... emphasis on writing.

A) single    B) only    C) particular    D) special

I chose D) He placed special emphasis on writing.

However, the key says the correct answer is C) "particular emphasis".

My dictionary says both words can be used: "put / place particular / special emphasis". Moreover, there is an example sentence in it: "He spoke with special emphasis on the subject of civil rights."

I am confused. Can you explain the difference to me?