The sun’s rays falling upon photo-electric cells, the whole apparatus will automatically go into operation.
举一反三
- When the sun's rays hit the earth, a lot of heat is __________ back into space. A: considered B: impressed C: eflected D: affected
- Ultraviolet rays from the Sun can cause which of the following?
- We need to look at the ________ of the whole aid operation.
- 1，On the day of first frost,the Sun's rays reach an angle of_______ degrees to the earth. A: 210 B: 220 C: 200 D: 230
- The domestic electric ______ promise to free the housewives from the burden of the hard housework. A: apparatus B: appliances C: instruments D: equipment