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: 'an intersection shows  an expanse of empty road and then a car coming out from under a large arch that looks like a giant chinese letter and stands between two buildings that stand at the forefront of am open walled walkway and retail venues'. How many words start with the letter 'o' in the sentence.