Final answer:
The Piper PA-44 Seminole has a twin-engine configuration and slender wings, and a T-tail. The Diamond DA-42 shares a similar appearance to the Seminole but has a much skinnier fuselage.
Step-by-step explanation:
The Piper PA-44 Seminole is distinguished from the PA-34 Seneca and Baron by its twin-engine configuration and slender wings. Unlike the PA-34 Seneca and Baron, the Seminole has a T-tail, which is indicated by option a. In terms of the aircraft that shares a similar appearance to the Piper PA-44 Seminole, but has a much skinnier fuselage, the correct answer is option a, the Diamond DA-42.