Embedded operating system has gone through four stages: No operating system, simple operating system, real time operating system, and Internet oriented operating system.

The brother and the sister walk to school. A: at hand B: hand in C: hand in hand D: on one hand

hand in hand

You should make the most of the opportunities( ). A: in hand B: at hand C: by hand D: with hand

The police came and they soon got the situation well （） A: by hand B: in hand C: on hand D: with hand

Having the right equipment __________ will be enormously helpful. A: hand back B: hand in C: hand on D: at hand

Could you______these books______, please? A: hand in B: hand out C: hand back D: hand at

We were asked to ______ our essay in three days. A) hand over C) hand in B) hand out D) hand down A: We were asked to ______ our essay in three days. B: hand over C: hand out D: hand in E: hand down

If you happen not to have anything _____________, could you please give me a helping hand? A: in hand B: by hand C: on hand D: out of hand

The teacher went into the classroom, _______. A: with book in hand B: a book in hand C: with a book in hand D: book in hand