Is the group of words a simple sentence, a compound sentence, or a run-on sentence?

This is very hard that is much softer.

A.
run-on sentence

B.
compound sentence

C.
simple sentence

Question

Is the group of words a simple sentence, a compound sentence, or a run-on sentence? 


This is very hard that is much softer.
 
 A.
run-on sentence
 
 B.
compound sentence
 
 C.
simple sentence

anonymous · Answer

Again it's A, runon sentence. 

If it was compound or simple, it would grammatically be correct, but this isn't. FE, if it was 'This is very hard, but that is much softer' or 'This is very hard; that is much softer' it would be compound.

So yes, it's a run-on unless I'm utterly mistaken :)