_______,when Marx was already _______,he found it was important to study the situation in Russia, so he began to learn Russian.

I have finished a large part of the book, the rest of which___ more difficult.

Having checked the doors were closed, and ______ all the lights were off, the boy openedthe door to his bedroom[ ]

_Can you write a letter inEnglish? _No, I______.I knowonly a little English.

The first quarrel between a young couple is the beginning of a new stage, ______ poetic love is transformed into practical life.[ ]