tenses

Surfing the internet (1) _______________ (become) a part of our daily life. How much do you (2) _______________ (know) about the internet?

The internet (3)_______________ (be) a network of millions of computers linked together by telephone lines, satellite and microwave connections. It (4) _______________ (start) by the United States Department of Defence in 1969. At that time, it (5) _______________ (allow) information to move freely around a military computer network.