37.5% of 24% of 840 = y + 12.6, then find the sum of

The MNC recently roped in a new head of the HR department.

Everyone knows that (1)/ the Earth revolves around the sun, (2)/ but there are still some people (3)/ who denies it. (4)

Identify the erroneous part of the sentence.

No sooner had the officer entered the room / when / the employees stood up / in silence.

They are looking forward (A)/to meet (B)/their parents. (C)

I used (A)/ a pair of black trousers(B)/ for a week.(C)

Select the segment which has a grammatical error in the given sentence. If there is no error ,select ‘no error.

I drink rather late last time 

Parts of the following sentence are given as options. Identify the segment that contains a grammatical error.

Debt bondage and forced labour flourish (A)/because the Government has (B)/do nothing to ensure (C)/the economic security of labourers (D).