We need to ensure the correct preposition has been used in each of the sentences.
Let’s identify the incorrect sentences before marking the options that are grammatically correct.
1 uses the incorrect preposition of time. The correct expression is ‘the exam will begin at 2:00 p.m. on January 8th.’
2 is incorrect as there is a redundant word. ‘Entered’ means get into a building or a room etc. ‘Enter into’ is a redundant expression.
The correct expression is ‘while entering the college building, he saw the statue of Mahatma Gandhi.’
Statements 3 and 4 are correct.
5 uses an incorrect preposition. The correct expression is Amitabh Bachchan is married to Jaya Bachchan.
6 is correct
So 3, 4, and 6 are the correct statements and D is the correct answer.