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.