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

Input: Consider Input: Sentence: 'a close up of a tennis player with a scary mask on'. Count the occurrences of the word 'a' in the given sentence.

Output: 3

Input: Consider Input: Sentence: 'a couple of zebras walk into a open area'. Count the occurrences of the word 'walk' in the given sentence.

Output: 1

Input: Consider Input: Sentence: 'a person is riding a bicycle but there is a train in the background'. Count the occurrences of the word 'a' in the given sentence.
Output: 3