which sentence is correct when direction is given to convert the sentence into positive degree?

sentence- He is the tallest boy in the class.

1.No other boy in the class is as tall as him.

2.No boy in the class is as tall as him.

3.No boy in the class is as tall as he is.

4. No other boy in the class is as tall as he is.

plz answer according to the syllabus and rules of icse grammer