✔ 最佳答案
1.They had (have) lost their way.=They were lost .
2.The helicopter cannot/can't see them.
3.They want to help.(Better:They want to offer help)
4.They are (in present tense) walking on the hill.
thank! (It should be either thankS or thank you)
Actually when using "have +present participle" e.g have bought or "had +past participle" e.g.had bought , it depends on whether past tense or present tense is used in the whole passage.
English is not a very difficult subject or language to learn,all you need to do is speak more,read more and write more.Don't be afraid to make mistakes,you have to learn from the mistakes.
Hope that i can help you~~^-^