I find __________ very difficult to learn English well .

This is not my book. It is .

Does anyone know _______ girl with a book in her hand over there?—I’m afraid no one knows.

Green economy offers a new model ________ people could both protect the climate and develop the economy, according to what Li said at the International Cooperative Conference on Green Economy and Climate Change.

I can’t go _____ because I have to go home at once.