Electronic Systems Design: Hands-on Circuits and PCB Design with CAD Software

A: A feels right because an open TVS removes the clamp and the DC/DC sees the full pulse. That's real. C tempts you if you're thinking EMC first, but the emissions angle is secondary to the electrical stress and doesn't hinge on the TVS being present or not. D matches field behavior at 40,000 km; electrolytics hate repeated excursions. B breaks down because reverse battery is handled by topology choices like series FETs or diodes, not by a unidirectional TVS that only wakes up on positive surges.

A: A lines up with IPC-2152 data for external copper and a modest rise. B sounds disciplined but quietly shifts two bases: internal layer and doubled temperature rise. C is the classic trap of grabbing IPC-2221; it underestimates width and has burned plenty of boards in the field. D feels conservative, yet it stacks an internal-layer assumption with an arbitrary factor and overshoots what the physics needs.

A: A fits if the board lived underhood with direct salt exposure, which it doesn't. B shows up early as assembly fallout, not as a mileage-driven field trend. D scares people in high-reliability circles, yet whiskers need compressive stress and time, not humidity plus bias. C matches the cabin environment: moisture, contamination, and voltage gradients quietly growing conductive paths until the failure pops.

A: A hits the contract between schematic intent and physical copper. B sounds tidy but ignores why designers separate nets logically even when copper touches. C confuses net ties with safety isolation rules from another world. D is a half-truth that skips context; sometimes it's right, sometimes it isn't, and the drawing explicitly asked for control that never made it to layout.