Why can writing your thoughts be an advantage over speaking them?
a. writing is more difficult for readers to remember.
b. writing makes it easier to reread, revise, and reconsider your thoughts.
c. writing makes it easier to answer all the audience's questions immediately.
d. writing is more casual and spontaneous.

B: Writing makes it easier to reread, revise, and reconsider your thoughts.

Explanation:

 Speaking is more spontaneous and it is connected with emotions. Writing your thoughts is an advantage over speaking because it helps to register ideas and thoughts in order to be able to reflect on them later on. This action may bring new ideas even at the time of writing them, and, certainly it provides a chance to confirm or change the original thought.

because each is self-sufficient.