What is meant by the most restrictive type in C?

Question

The book The C Programming Language talks about \"the most restrictive type\" in section 8.7, Example — A Storage Allocator:

A

Answer 1

I think that the quote means the most restrictive alignment of types. For example char is the least restructive type if to follow this logic. An object of type char does not impose a constraint on its alignment while for example type int has alignment requirement of usually 4 byte bounds. Thus int is a more restrictive type than char.