(1) (how/been/this / have / we /is) destroying the environment.
This is how we have been.
destroying the environment.
(2) John is (in / where / happy/be/to/Japan,) he has always wanted to come.
John is
...happy to be in Japan, where
he has always wanted to come.
3) (an age / believed / there /when/ was / people) that the sun went around the earth.
1. There was an age when people believed that the sun went around the earth.
4) Many people feel depressed (Monday morning, /to/ have/on/when/they) return to work.
Many people feel depressed Monday morning when they have,
on
return to work.
to on