49 CFR 192, 192.303 Each transmission line or main must be constructed in accordance with comprehensive ______ that are consistent with 49 CFR 192.

According to 49 CFR 192.303, "Compliance with specifications or standards," each transmission line or main must be constructed in accordance with comprehensive written specifications or standards that are consistent with 49 CFR 192.

The final answer is $\boxed{\text{a. Written Specifications or Standards}}$