Read the sentences.

as a child, thomas edison asked an endless number of questions. his teachers found that he did not answer the questions they asked.

which shows the correct coordinating conjunction for combining the sentences?

a as a child, thomas edison asked an endless number of questions, but his teachers found that he did not answer the questions they asked.

b as a child, thomas edison asked an endless number of questions, or his teachers found that he did not answer the questions they asked.

c as a child, thomas edison asked an endless number of questions, and his teachers found that he did not answer the questions they asked.

d as a child, thomas edison asked an endless number of questions, so his teachers found that he did not answer the questions they asked.