​Identify the part which contains an error.​

Correct option is C

The error lies in option (c) “not to be”. The phrase “too good not to be true” is incorrect due to the double negative structure that causes confusion in meaning.

Let’s analyze:
The correct idiomatic expression is:
“too good to be true”, which means that something seems so perfect or excellent that it is hard to believe it’s real or genuine.

In the sentence given:

“This news is too good not to be true”
the use of “not to be true” creates a logical inconsistency, suggesting the news is so good that it must be true, which contradicts the standard usage. The original phrase implies skepticism, not certainty.

Therefore, the correct sentence should be:

“This news is too good to be true.”

The part “not to be” should be revised to “to be” for the sentence to be grammatically and idiomatically correct.