Meaning of 'test card'

[puspa]

Test No. incompl/inter-59 "Testing, Testing", question 10

In order to make sure that your television is tuned properly there is a coloured test ......... on the screen.

(a) paper
(b) sheet
(c) place
(d) card

Test No. incompl/inter-59 "Testing, Testing", answer 10

In order to make sure that your television is tuned properly there is a coloured test card on the screen.

Correct answer: (d) card

Your answer was: incorrect
In order to make sure that your television is tuned properly there is a coloured test sheet on the screen.
_________________________

Why is it card??
thanks

[Torsten]

Because a test card which is also known as a test pattern in North America, is a television test signal. A test sheet could be a piece of paper that contains test questions you have to answer in an examination.

TOEIC listening, photographs: A moving truck