Which one of the following is the hardest cutting tool material ?

back rake and side rake

There are two rake angles of a lath cutting tool. These are back rake and side rake.

any one of positive, negative or zero

Rake angle of a lathe tool can be positive, negative or zero.

Positive rake angle

Positive rake angle a lathe cutting tool makes it sharp and pointed.

Reduces friction

Since negative rake angle of a lathe cutting tool increases area of contact, in increases the friction between the work piece and the cutting tool.