After creating an anonymous pipe, how can a process send a message via the pipe?

Question $4$ Select one:

a$.$

The process can store any integer value in the file descriptor for the writing end of the pipe.

b$.$

It can use the write$()$ system call.

c$.$

There's a send$()$ system call for sending messages.

d$.$

It can use the read$()$ system call.