What equipment is not required for this flight?

Above the Class C still counts

Allentown's airport, Lehigh Valley International (ABE), sits inside Class C airspace. At 5500 you're above its ceiling, so it's tempting to think the Class C rules no longer apply. For two pieces of equipment, they still do.

91.215(b)(4) requires a transponder with altitude reporting in all airspace above the ceiling and within the lateral boundaries of a Class C, up to 10,000 MSL. 91.225(d)(3) uses the same words for ADS-B Out. A simple way to picture it: take the outer edge of the Class C on the sectional and extend it straight up to 10,000. Anywhere inside that column, you need both.

You'll find the ceiling printed on the sectional inside each Class C ring. It's worth knowing, but for this rule what matters is the lateral boundary.

ADS-B In is never required

ADS-B Out is what your airplane broadcasts so ATC and other aircraft can see you. ADS-B In is what you receive: traffic and weather on a panel display or tablet. It's a great safety tool, and plenty of renters carry a portable receiver for it. No regulation requires it, which makes B the answer.

Anticollision lights in a 172S

91.205(b)(11) requires an anticollision light system for day VFR in small airplanes certificated after March 11, 1996. Every 172S was built in 1998 or later, so the straightforward reading puts it on the required side.

There is a gray area here. The 172's type certificate dates from the 1950s on a CAR 3 basis, and the R and S models were added to it. In 2017 the FAA's Chief Counsel was asked about this rule on a Cessna 172 and laid out both readings without settling it. A pilot who takes the position that the lights aren't required by 91.205 still has to work through 91.213 to see whether something else requires them: the equipment list, the KOEL, the type certification. And since a 172S has them installed, 91.209(b) says they have to be on.

The transponder and ADS-B Out are separate rules

ADS-B Out didn't replace the transponder. 91.215 still requires the transponder, and 91.225 adds ADS-B Out on top of it. In many airplanes a single Mode S extended squitter transponder does both jobs, but the airplane needs both functions.