Construction on the tunnel had begun in 1988,and the tunnel opened for passengers in 1994.whats mistake in this??

Question

whats mistake in the above mentioned question

Answer 1

Construction on the tunnel had begun in 1988, and the tunnel opened for passengers in 1994.

You have a confusing choice of tenses here. When using the past perfect, (the past of the past) you need to have some context for when we're talking about. For example:

What I arrived, the concert had begun already.

The first verb gives context for when this "past in the past" is staged. The second is telling the listener that the concert had already started by the time "I" arrived. The tense requires both to make sense.

----

The sentence you have above would be significantly more natural if you simply used the past simple tense like what I have below:

Construction on the tunnel began in 1988, and the tunnel opened for passengers in 1994.

This fixes all of the grammar errors, but there is also a concept in English where we try to not repeat the same words. This part is option as it isn't critical to understanding, but it does make it sound closer to a native-speaker. We try to use varying vocabulary as well as sentence structure to do this. To make this sentence as natural as possible, I would say:

Construction on the tunnel began in 1988, and reopened for passengers by 1994.

Either one will work and get the point across, but the second one sounds closer to what a professional native speaker would say.