You can study the grammar _____ memorizing it.[ ]

_____frightened us ____the electricity was suddenly cut off, which threw all of us into the dark.

The boy said ________ couldn’t he work out the problem but his teacher didn’t know how to do it.

Take care! Don’t get the oil on your clothes, for it _______ easily.

The old man was so_______ the good news that he couldn’t say a word.