[Grammar] That what which

[Fourrier]

The planet is warming up, …. is worrying.
(A) that
(B) what
(C) which
(D) that which


A similar one :
The winter was so mild .… bears could
not hibernate.
(A) that
(B) as
(C) than
(D) so that

Justification: I have a feeling that is the right answer

 

[Mehrgan]

The planet is warming up, …. is worrying.
(A) that
(B) what
(C) which
(D) that which


A similar one :
The winter was so mild .… bears could
not hibernate.
(A) that
(B) as
(C) than
(D) so that

Justification: I have a feeling that is the right answer

***not a teacher***
No, in the first one, "WHICH" is the correct choice as it refers to the whole idea "the fact that the planet is warming up."

In the second one, "THAT" is the correct one. "So that" can not be true, because it is used to introduce the reason, or outcome of an activity. If you choose "so that", your sentence would mean as "the reason why the winter was mild was that the winter wanted to stop bears hibernating!"...