Используйте правильную форму прошедшего простой пассивный или настоящего совершенного...

Question

Используйте правильную форму прошедшего простой пассивный или настоящего совершенного пассивного.
The radio......(invent)at the beginning of the 20th century .In the First World War ,radios ....(use)to communicate with soldiers. Since the 1960s,many radio signals......(send)into outer spaces.
So far,no answers....(receive)from other planets. It's possible that the signals have arrived on other planets,but the messages .......(not understand ).

Answer 1

The radio (was invented) at the beginning of the 20th century.
In the First World War, radios (were used) to communicate with soldiers. Since the 1960s, many radio signals (have been sent) into outer spaces.
So far, no answers (have been received) from other planets.
It's possible that the signals have arrived on other planets, but the messages (were not understood).