Explanation

We need a relative clause referring to "students" (a plural noun).

There were many students who knew all the answers.

- "who" is the correct relative pronoun for people  

- "knew" matches the past tense and plural subject "students"

Explanation

Look at the sky. It *is going to rain.*

We use "is going to" for predictions based on present evidence — in this case, seeing dark clouds in the sky.

Explanation

Can anyone give me a hand, please, because I have fallen over?

- "Give me a hand" is an idiom meaning help me.

- We use "a hand" (not "the hand" or "an hands") because it's the correct article + singular noun structure.

Explanation

I have been thinking for hours, but I am yet to arrive at a decision.

- "Yet to arrive" means something has not happened up to this point, which fits the context.  

- "Still" is incorrect in this structure.  

Explanation

Please do no interfere in my personal affairs. 

Explanation

Why did you give me such a large serving of potatoes?

- "Such a" is used before adjective + singular countable noun:  

Explanation

“If you like” is used to give permission or choice politely.

The sentence reads correctly as: “You can go home now if you like.”

Explanation

The correct subject form is “My mother and I”, not “me and my mother.”

The past tense “decided” properly matches the narrative context.

Explanation

“But” is used to show contrast between past inability and present ability.

The sentence correctly reads: “I couldn’t swim when I was a child, but I can swim now.”

Explanation

The phrase "a rich man was on his deathbed."

It is a standard opening used to describe a wealthy character who is dying and about to give advice or a will.