Select the most appropriate option to substitute the bracketed segment in the given sentence. If there is no need to substitute it, select 'no substitution required'. (In fact, climbing fern is spreading so rapidly that its) now the state's worst invasive weed.

A

In fact, climbing fern is spreading so rapid that it's

B

In fact, climbing fern is spread so rapidly that its

C

In fact, climbing fern is spreading so rapidly that it's

D

No substitution required