By Rachel Mitchell Text Copyright 2018 by Rachel Mitchell

Breakthrough [Noun] (an important achievement or development that comes after a lot of hard work).
Scientists are claiming a major breakthrough in the fight against cancer. A technical or scientific breakthrough is necessary.
To become obsolete [Verb] (to be no longer used because something new has been invented).
The machinery has become obsolete.
The invention of email has made hand-written letters obsolete.
To be out of one’s depth [Expression] (something that exceeds one's knowledge or ability because it is too difficult).
The lesson was very hard, and he was completely out of his depth. She felt totally out of her depth in her new job.
To become over-reliant on [Expression] (to need something too much for your survival or success).
We have become over-reliant on technology so much so that we cannot even imagine living without it.
Nowadays, people become over-reliant on Facebook to fulfill their social needs.
To be for the better [Expression] (in a way that improves the situation).
These changes seem to have been for the better.
My teachers' influences have been for the better, and I am wholeheartedly grateful for that.
LETTER C
Combination [Noun] (a mixture of two or more things are combined to create something new).
A clause is the combination of a subject and a verb.
The combination of science and art classes helps students learn in a creative way.
A clause is the combination of a subject and a verb.
A combination of several mistakes led to the accident.
Come across [Verb] (to meet or find something or someone by chance). While she was cleaning out her desk, she came across some old pictures. I never came across such a big snake in my life.
Catch one’s eye [Expression] (to attract someone's attention).
A beautiful dress caught her eye while she was walking through the market.
A small shop selling lovely necklaces caught my eye while I was driving down the road.