Read the two sentences.

I listened to the birds singing. I read a book on the patio.

Which sentence combines the two sentences using a present participle?

a) I listened to the birds singing, and I read a book on the patio.

b) While I listened to the birds singing, I read a book on the patio.

c) Listening to the birds singing, I read a book on the patio.

d) I read a book on the patio while I listened to the birds singing.