Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks.

The Internet has truly transformed how students do their homework. (1)______ homework today still means spending time in the library, it’s for a different reason. Rather than using books for research, students today are (2)______ to the Internet to download enormous amounts of data available online.

In the past, students were limited to their school’s (3)______ of books. In many cases, they got to the school library and found out that someone had already taken the books they needed. Nowadays, such inconvenience can be avoided since the Internet never runs out of information. Students, however, do have to

(4)______ sure that the information they find online is true. Teachers have also benefited from the homework which is done on the Internet. They do not need to carry students’ papers around with them any more. This is because online (5)______ allow students to electronically upload their homework for their teachers to read and mark. Of course, this also means that students can no longer use the excuse that the dog ate their homework!

Điền vào số 5

A. materials

B. systems

C. structures

D. sources