(1) If it will snow tomorrow, we will have to leave home early.
(2) If you get home, please call me. → When
(3) If I were you, I will apologize to the teacher. → would
(4) If you asked me first, I could have savedyou the trouble.
→ had asked
(5) If I passed the exams, I would be a college student now.
→ had passed
（解答） f Hillary visites [call on] me while [when] I am out, could you give her this message.
（別解） If hillary should come here in my absense, could you gibe her this message?
（解答） If we succeeded [could succeed] in everything, we would feel that (our) life is boring.
（別解） If we succeeded in whatever we do [did], we might feel that life is dull.
（解答） If it rains (on) that day, I will pick you up at the station.
（別解） If it should rain that day, I would [will] pick you up at the station.
（解答） When you are as old as I am [When you are as old as me], you will be able to understand what I have (just) told you.
（別解） When you are my age, you will understand what I have (just) said.
（解答） If Ryan had been more careful, we would not have take the wrong bus.
（別解） If Ryan had taken more care, we would not have got on the wrong bus.
（解答） If I had passed [succeeded in] the interview (test) (that / which) I had when I was young and been able to study abroad [to syudy overseas / to go abroad to study], my (later) life would have been completely different.
（別解） If I had passed an interview and studied abroad when I was young, my life would have changed completely.
(2) 日本列島の温度が平均一度上がると、全国の電気需要が350万ワット増えるそうだ。（解答） It is said (that) supply and demand for electricity will increase by 3.5million watts when the average temperature in Japan rises by one degree.
（別解） It seems that if the temperature of Japan goes up by one degree on average, people will use 3.5 million watts more electricity nationwide [throughout the country].
（解答） If everyone thanked and considered those [the people] around them and expressed in words how they felt, many [a lot of] people would be less likely to feel stressed.
（別解） If each of us felt gratitude towrds and concern for those around us and expressed this in words, many people would have less stress.
（解答） I hear [have heard / heard] (that) there are many languages in the world with no writing system [without a writing system]. We read and write everyday, so we think (that) it would be (very) inconvenient [difficult] to live without written words.
（別解） It seems that there are a lot of language in the world that have no writing system. We use writing everyday, so we think (that) such languages mut be useless.
（解答） If you can (clearly) explain to a doctor (accurately) how you feel when you get ill in a foreign country, your language ability is perfect.
（別解） Suppose that when you go abroad and become ill, you can tell doctor (exactly) how you feel in a foreign language. This shows [proves] that your skill in that language is excellent.
I agree tha smoking should be made illegal in Japan for the following reasons.
Firstly, smoking is extremely harmful to the health when cigarettes burn； they generate more than 7000 chemicals, many of which are poisonous and at least 69 of which can cause canser. Passive smoking is even more harmful, and 37 percent of lung cancer in wives is cused by their husband's smoking. Perhaps we have the right to choose what we put into our bodies, but do we also have the right to destroy the health of those around us?
It is particularly important for Japan to make smoking illegal now, as an increasing number of tourists are visiting this country. They will otherwise be shocked at how smoky restaurants and bars in Japan are, when no-smoking policies have become the norm among advanced nations.