1)put the verb in bracket in present simple,present continious,past simple ,past continuous or present perfect 1)) ) his knee as he )2)luke ) hard for the last three weeks.3))at the volcano as (flow) down during the eruptin last night.

1) John (tripped) and (cut) his knee as he (was walking) up the volcano.
2) Martin (hasn't reached) the crater yet.
3) Look at the volcano. Huge rocks (are exploding) out of the crater.
4) They (are going) volcano surfing tomorrow.
5) Luke (has worked) hard for the last three weeks.
6) We (are leaving) for Chile next Monday.