She remembered several occasions in the past            she had experienced a similar feeling.

There is a natural phenomenon      scientists call the greenhouse effect.

Do you remember the chicken farm _____ we visited three months ago?

Is _______ some German friends visited last week?

His teacher is the only one ______ he can turn when he is in trouble.

The most important thing_______we should pay attention to is the thing_______I have said.

He's got himself into a dangerous situation ______he is likely to lose control.

There is a natural phenomenon      scientists call the greenhouse effect.

The girl went to have piano lessons at the training center with her sister      she would stay for an hour.

Cheer up! Everyone may have periods in their lives    everything seems tough．