J.R. S. answered 03/27/20
Ph.D. University Professor with 10+ years Tutoring Experience
The problem is with using the term "all". That makes your classmates statement false. Here are examples.
Ammonia (NH3) contains THREE hydrogen atoms, but yet it is not an acid. When in water, it is a base.
Phenol (C6H5OH) contains an -OH group, yet it is mildly acidic.