Please check if the rewritten sentences are right

Rewrite the following sentences using 'it' in the beginning as a preparatory subject:-

A. To make mistakes is easy.

It is easy to make mistakes.

B. To wait for people who were late made him angry.

It made him angry to wait for people who were late.

C. My ambition was to retire at thirty.

It was my ambition to retire at thirty.

D. Your task is to get across the river without being seen.

It is your task to get across the river without being seen.

E. For you to ask Smith would be a big mistake.

It is a big mistake for you to ask Smith.

Please check whether the rewritten sentences are right. It's a task from a model test paper

Thanks in advance