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.

[EX Q]: Sentence: 'a guy a skateboard jumping in the air'. How many words start with the letter 'a' in the sentence.
[EX A]: 3

[EX Q]: Sentence: 'dusty train passing through a dry mountain valley'. How many words start with the letter 'd' in the sentence.
[EX A]: 2

[EX Q]: Sentence: 'a surfer stands up on a surfboard and rides a wave while another paddles towards shore'. How many words start with the letter 's' in the sentence.
[EX A]:
4