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 tennis player swings his racket on a serve'. How many words start with the letter 'o' in the sentence.
1

Sentence: 'a group of four skiers are getting ready to embark'. How many words start with the letter 'g' in the sentence.
2

Sentence: 'a man eating a donut by a big window'. How many words start with the letter 'a' in the sentence.

3