(1) I will be back after two hours. → in
(2) I got a new pencil case for the first time in long time.
→ in a long time [in ages / in years]
(3) Until you reach twenty, you must get a driver's license.
→ By the time
(4) Mr. Yang will be away by Monday night
→ until / till
(5) We got to the station before ten minutes our train left.
→ ten minutes before
（解答） It started [began] to snow [snowing] (about) twenty minutes after we arrived at [go to] school.
（別解） We arrived at school (about) twenty minutes before it started to snow.
（解答） Matthew will (be able to) leave (the) hospital in two weeks.
（別解） Matthew will (be able to) leave (the) hospital two weeks from now.
（解答） Please make sure (that) you get to [come to] the airport t least one hour before departure.
（別解） Please be sure to get to [come to] the airport at least an hour before the flight.
（解答） The rice harvest [The harvest of rice] this year seems to be [seems like / is likely to be] the best in five years.
（別解） It seems that this year's rice harvest will probably be the best in five years.
（解答） Could you keep an eye on [keep your eye on] this suitcase until [till] I get back [I am back / I return]?
（別解） Would you mind watching this bagage until I get back?
（解答） The evening news on TV [The TV evening news] says [said] (that) Tokyo had the heaviest snow [the most snow / the heaviest snowfall] in ten years.
（別解） According to the evening news on TV, Tokyo had the heaviest snow in ten years [they had the heaviest snowfall in ten years in Tokyo].
（解答） I visited my hometown for the first time in fifteen years, but [and] I found no buildings that [which] reminded me of my childhood.
（別解） When I visited my hometown for the first time in fifteen years, (I found that) there were no buildings that [which] reminded me of my childhood.
（解答） WHO [The World Health Organization] estimates that there are 1.6 billion [one billion six hundred million / 1,600 million] obese adults in the world [all over the world]. It is expected [estimated] that this number [this figure] will increase by 40 percent [by forty percent] in the next decade [over the next ten years / in ten years].
（別解） According to WHO, there are sixteen hundred million overweight adults all over the world. This number is expected to increase by forty percent in the next ten years.
（解答） I have to [need to] revise and submit [hand in / turn in / give in] the composition to Professor Brown by eight (o'clock) in the morning (tomorrow) [by eight (o'clock) tomorrow morning].
（別解） After correcting (the mistake of [in]) the [my] composition, I have to submit it to Profrssor Brown by 8 a.m. tomorrow.
（解答） By the time you (somehow manage to) have enough money and time, you have (probably) become quite old. Even if you take [go on] a cruise you are looking forward to, it is difficult [hard] to act and think as you would like to [as you want to / as you wish].
（別解） It is not until you are very old that you have enough money and time to ravel by ship. Even if you take a cruise you are looking forward to, you cannot control your body and mind as you would like to.
Due to the problem of global warming, all vehicles will be powered by electricity or hydrogen. There will be an automated safe-traffic system so we will no longer have to drive our cars, but only have to input our destination into car's computer. Roads willbe safer and unpolluted, so more people will use bicycles in cities. （58語）