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 girl and her dog walk past a bike'. How many words start with the letter 'a' in the sentence.
3

Sentence: 'a black and white cat sits in a bathroom sink'. How many words start with the letter 'a' in the sentence.
3

Sentence: 'a white bathroom has a striped shower curtain'. How many words start with the letter 'b' in the sentence.

1