Not until all the fish died in the river, _________ how serious the pollution was．

did the villagers realize

the villagers realized

the villagers did realize

didn't the villagers realize

Many people stood near the bus stop, nervously waiting _________．

to pick up

picking up

to be picked up

being picked up

I would love _________ to the party last night but I had to work extra hours to finish a report．

to go

to have gone

going

having gone

The boy wanted to ride his bicycle in the street, but his mother told him _________．

not to

not to do

not do it

do not to

Paul doesn't have to be made _________．He always works hard．

learn

to learn

learned

learning

The mother didn't know _________ to blame for the broken glass as it happened while she was out．

who

when

how

why

The purpose of new technologies is to make life easier, _________ it more difficult．

not make

not to make

not making

don't make

The weather here in spring is much similar to _________ in my hometown．

one

it

that

this

It is said that some software on learning subjects for pupils _________ in a very practical way．

designed

is designed

designs

is designing

The pictures always remind me of those unforgettable memories _________ we had a lot of fun together in our childhood．

what

when

that

where