In this task, you need to count the occurrences of the given word in the given sentence.

Sentence: 'a woman is riding a wave on a surfboard'. Count the occurrences of the word 'a' in the given sentence.
3

Sentence: 'side review mirror shows dog hanging its head out the window'. Count the occurrences of the word 'the' in the given sentence.
1

Sentence: 'herd of happy zebras in a field of grass'. Count the occurrences of the word 'grass' in the given sentence.

1