Question

2.
In which sentence does a noun clause function as the subject?



Bring extra calculators for whoever forgets to bring theirs along.


Whoever understands how to multiply and divide numbers by 10 can easily use the metric system.


Before the math competition, be sure to memorize whatever formulas you will need.


We practice after school in whichever rooms have the most board space for our work.

Answer 1

Sentence 2.

"Whoever understands how to multiply and divide numbers by 10" is a noun clause functioning as the subject of the verb phrase "can easily use the metric system." The other sentences contain noun clauses as objects (direct objects or objects of prepositions), not subjects.