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

Example Input: Sentence: 'a colorful hydrant  sitting in the grass on a quiet street'. Count the occurrences of the word 'a' in the given sentence.
Example Output: 2

Example Input: Sentence: 'a group of elephants marches down the city street in front of a large building'. Count the occurrences of the word 'a' in the given sentence.
Example Output: 2

Example Input: Sentence: 'a street sign with a bicycle on it beside a street'. Count the occurrences of the word 'a' in the given sentence.
Example Output:
3