[单选题]
A single narrow slit of width $b$ is used to diffract the radiation of a microwave transmitter. A receiver is positioned at distance of $D$ from the slit. The receiver is moved from point $A$ to point $C$. At point $B$, the intensity of the radiation is minimum for the first time.
Which of the following changes could cause point C to be the first occurrence of a detected radiation minimum?
I. Increase D
II. Decrease slit width
III. Replace the microwave transmitter and receiver with a radio wave transmitter and receiver
A. Only $I$
B. Only $II$
C. $I$ and $II$ only
D. $I$, $II$, and $III$
