Why would anyone choose the unreliable protocol?
UDP drops the safety net on purpose. Here's the one thing it buys you that TCP never can.
The question
Why do voice and video calls prefer UDP over TCP?
The answer
B UDP avoids retransmission delay
A retransmitted voice packet arrives too late to be useful, so TCP's safety net just adds delay. Don't fall for C, UDP guarantees nothing about order.
Why it trips people up
Most courses teach TCP as the 'good' protocol and UDP as the compromise. In practice the choice is about what failure looks like: TCP hides packet loss by retransmitting, which is invaluable for a file and useless for a live call, where a late packet is simply wrong. Pick the protocol whose failure mode your application can live with.
Exam tip
Read what the question is actually asking before looking at the options. The wrong answers here are ones candidates genuinely pick — each is true of something adjacent, just not of what was asked.