Which sentence shows an example of an object pronoun? They were all so happy to be at the beach and to dig in the sand.
Suzy noticed the strength of the waves and felt them growing stronger every minute.
She found some beach balls and threw one directly to Rusty.
He noticed his shoulders were getting pink, so he rubbed on sunscreen.

B.

Explanation:

An object pronoun can be defined as a word which replaces a noun in a sentence. An object pronoun tends to serve as the object of a verb or preposition in the sentence. It is also known as objective pronoun.

From the given options, the statement which exemplifies an object pronoun is 'Suzy noticed the strength of the waves and felt them growing stronger every minute.' In this sentence, waves, a noun, is being replaced by pronoun them. The word 'them' is also serving as an object of the verb 'felt' in the sentence.

Therefore, option B is correct.