How is the underlined gerund used in the sentence?

Her hobby in the springtime is gardening.

A.
direct object

B.
object of a preposition

C.
subject

D.
predicate nominative

Question

How is the underlined gerund used in the sentence? 

Her hobby in the springtime is gardening.
 
 A.
direct object
 
 B.
object of a preposition
 
 C.
subject
 
 D.
predicate nominative

anonymous · Answer

THE WORD IS WALKING

nightwielder · Answer

We should skeleton the sentence:
Her hobby is walking.
Further simplified:
Hobby is walking.
Subject is "hobby", verb is "is"
"walking" is directly the object as evident in the skeleton.
A is the answer.
BTW I kinda invented the word skeleton or i might have heard it from somewhere.
And this is math section