<span>1) Scientists have produced (pres perf - </span><span>produce) a stable chemical compound to store the energy.
2) The support of some boilers is (pres simp - be) on bottom.
3) First pressure stage of the impulse turbine can deal (pres simp - can) </span><span> deal (unfinitive</span><span><span><span> - deal </span>) </span>with a large energy drop.
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The new computer is faster than the old one
Our house is older than my scholl's building
My schoolbag is heaver on Tuesday than on Friday
2.When we saw the landslide, we were driving home.
3.She was skiing when she heard the avalance.
4.The rescue helicopter arrived when the family was phoning for help.
5.A fire fighter gave them water when they were waiting for an ambulance.
6.I was drinking from my water bottle when i saw a helicopter.