Identify the type of error in sentence: The reason we are early is because my watch is fast.

A. Definition structure

B. Explanation structure

C. Parallel structure

D. Dangling construction

E. Correct

The type of error in the given sentence is the explanation structure. The correct answer is option B. The issue in the sentence is redundancy. When the word "reason" is already stated, the word "because" should be omitted. The word "because" is a conjunction that already explains a reason. Therefore, the correct sentence should either be:

a. The reason we are early is that, my watch is fast.

or,

b. We are early because my watch is fast.