Consider the following statement (s) about Doppler Effect. I. Johann Christian Doppler, an Austrian physicist first proposed Doppler effect in 1842. II. Doppler Effect is observed that the pitch of the sound is higher when we approach a stationary source of sound with high speed. Which is/are correct statement (s) is/are correct?

Consider the following statement (s) about Doppler Effect. I. Johann

1.	Consider the following statement (s) about Doppler Effect. I. Johann Christian Doppler, an Austrian physicist first proposed Doppler effect in 1842. II. Doppler Effect is observed that the pitch of the sound is higher when we approach a stationary source of sound with high speed. Which is/are correct statement (s) is/are correct?
A.	Only I
B.	Only II
C.	Both I & II
D.	All of the above
Answer» D. All of the above