He acquired Swiss nationality (20) in 1901 and he began working at the Swiss patent office the next year.

Correct the following sentence..
in 1901 and

A.in 1901 and,
B.in 1901, and
C,in 1901, and,
D.no error
I think it is D...?

There is an error. A comma is needed to separate two independent clauses.

Then I would say B and place it after 1901...?

Did this post twice - sorry

That's right. A comma is placed after 1901.

I understand why...thank you

To correct the sentence, we need to determine if a comma is needed after "in 1901". In this case, a comma is not necessary because the phrase "in 1901" is not providing additional information or separating any clauses. Therefore, the correct answer is D - no error.