対象-2: 年賀状の配達は、高校生に人気のアルバイトです。

Excite!&@nifty:
The delivery of the New Year's card is a popular part-time job among the high school student.

Livedoor:
Delivery of a New Year's card is part-time job popular with a high school student.

Yahoo!:
Delivery of the New Year's card is the part-time job that is popular among high school students.

OCN:
A delivery of a New Year's card is a part-time job popular with high school students.

BabelFish:
Delivery of the New Year's greeting card is part-time job of popularity in the high school student.

Google:
Delivery of the New Year is a popular high school job.

Bing Translator:
Delivery of greeting is a part-time job of popular high school student.

Summary)
No systems use plural of cards.