Which of the following media types is LEAST likely to be affected by electromagnetic interference?

Coaxial cable uses a copper center conductor surrounded by shielding, which reduces but does not eliminate susceptibility to EMI.

Fiber optic cable carries data as modulated light pulses through glass or plastic strands, which are entirely unaffected by magnetic or electric fields in the surrounding environment. Because no electrical current flows through the medium, there is no mechanism by which external EMI can induce noise or signal degradation. This property makes fiber the preferred choice in electrically noisy industrial, medical, or high-voltage environments.

Wireless B (802.11b) uses radio frequency signals in the 2.4 GHz spectrum and is inherently susceptible to interference from other RF sources.

HSPA is a cellular wireless technology that transmits over radio frequencies and is therefore subject to electromagnetic interference and signal degradation.