Metal cables are used as telephone wires because?
A
they are cheap
B
they are sourced locally
C
the speed of sound in them is very low
D
the speed of sound in them is very high
Verified Correct Answer: D.
Physical Principles & Numerical Solution
The speed of sound is highest in solid.
Metals (solids) like copper, steel rod, etc
Source: WAEC / JAMB / NECO Classroom Archive (Record #14200)