In this task, you need to count the number of words in a sentence that start with the given letter. Answer with numbers and not words.

Sentence: 'a mother bear and her two young are crossing a shallow river'. How many words start with the letter 'a' in the sentence.
4

Sentence: 'two giraffes are walking down a rocky path'. How many words start with the letter 'a' in the sentence.
2

Sentence: 'a person wearing all white is crouched beside a traffic signal'. How many words start with the letter 'b' in the sentence.

1