The magician placed the ball (1)/underneath of his hat and (2)/ made a mystic sign above it.(3)/No - Error(4)

In the following questions, some part of the sentence may have errors. Find out which part of the sentence has an error and select the appropriate option. If a sentence is free from error, select .No error.. 
The magician placed the ball (a)/ underneath of his hat and(b)/ made a mystic sign above it. (C)/No error(d)

Death of (1)/ his only son (2)/ made Mohan desolate. (3)/ No error (4)

This errors (1)/ are made (2)/ by foreigners. (3)/ No error (4)

Find out which part of a sentence has an error

It is high time (1)/ that we leave (2)/ this place. (3)/No error (4)

One (1)/ should keep (2)/ his word. (3)/ No error (4)

It is else than (1)/his stupidity which stands (2)/in the way of his progress. (3)/No error (4)

Find out which part of a sentence has an error

He is a university professor (1)/ but of his three sons (2)/ neither has any merit. (3)/ No error (4)

In the following question, some parts of the sentences have errors and some are correct . Find out which part of a sentence has an error. If a sentence is free error, your answer is (d).
$\frac{\text{At his return}}{a}$ $\frac{\text{we asked him}}{b}$ $\frac{\text{many questions.}}{c}$ $\frac{\text{No error}}{d}$