Answer:
a. Subject.
Explanation:
A gerund is a verb with an '-ing' that functions as a noun in a sentence. And a gerund phrase is a phrase containing a gerund and the words modifying it.
In the given sentence "loading seven kids in a vehicle is no easy task", the gerund phrase is "loading seven kids in a vehicle". And the phrase functions as the main subject of the sentence.
Thus, the correct answer is option a.
