Passive Voice

Here are the materials which you kindly asked me to post: the exercise we did in class today.

1. Life on other planets …… (not find) yet.
2. On December 21st 2016, eerie lights in the sky …… (can/watch) by crowds of people in North America and Canada.
3. The whole day yesterday our reporter was at a very unusual scientific conference. The problems of space colonization …… (discuss) at that time.
4. Some people believe that in the future Mars …… (colonise) by people.
5. Watch our TV report on Professor Brighton’s speech at the conference.  Look!  A great number of strange objects …… (present) to the public. The public is out of breath.