Phrase "he was shrinking when"

[Anthonia]

English Language Tests, Intermediate level

ESL/EFL Test #263 "Irregular Verbs Test (11)", question 3

The little puppy looked like he was ......... when his owner scolded him for chewing the red slippers.

(a) shrink
(b) shrinks
(c) shrinking

English Language Tests, Intermediate level

ESL/EFL Test #263 "Irregular Verbs Test (11)", answer 3

The little puppy looked like he was shrinking when his owner scolded him for chewing the red slippers.

Correct answer: (c) shrinking
_________________________

what the answer?

Anthonia

[Lost_Soul]

You can say both:
The little puppy looked like he was shrinking
The little puppy looked like he was a shrink

But there is no indefinite article before "shrink", and therefore the only answer is "shrinking"