For the four-sentence (S1 to S4) paragraph below, sentences S1 and S4 are…

For the four-sentence (S1 to S4) paragraph below, sentences S1 and S4 are given. From the options P, Q and R, choose appropriate sentences for S2 and S3 respectively.

S1: Why do birds sing?

S2: _________

S3: _________

S4: The length and complexity of the song give information about the health of the bird.

Options:

P: Birds sing to warn other birds to stay off their territory.

Q: You might assume that birds sing because they are happy.

R: Birds also sing to find a healthy mate.