Verified Answer :

The answer is c because a drought is when there is a period of no water, ice age is when everything is ice and a draft doesnt make sense

AL2006

Well, I think it kinda depends on how long the "extended period" is.

If the extended period is a week, a month, or a few months,
then I'd call it a 'cold wave'.

If the extended period is like 100 years or more, then you're
starting to talk 'ice age'.