Air pollution will remain a problem for a long time, ______ we have done a lot to solve it.( )
though
since
unless
if
Cloth shoes became popular during the Ming Dynasty, ________ in Sichuan province.
hardly
nearly
really
especially
Rainbows ________ when sunlight passes through small drops of water in the sky.
produce
produced
are produced
were produced
Alice often ________ the fun of doing DIY with us. She is so creative!
shares
provides
makes
gives
The biggest challenge we all face is to prevent further environmental disasters. We ________ take action before it is too late.
can
must
may
might
Yuan Longping and his team have solved the problem of ________ for many people.
hunger
health
pollution
population