翻译句子，谢谢！！！

1.We try our best to assure the old man that it is safe to fly on air.
2.I can use the computer,but when it comes to mend the computer,I have on idea about it.
3.The job involves to go aboard three months every year.
4.He see to that this error will not happen .

1.We try our best to assure the old man that it is safe to fly on air.
2.I can use the computer,but when it comes to mend the computer,I have on idea about it.
3.The job involves to go aboard three months every year.
4.He see to that this error will not happen

1.We try our best to assure the nervous old man that travelling by air is safe.
2.I can use computers,but when it comes to mending them,I could not say a word.
3.This job involve the condition that one needs to be abroad 3 monthes a year.