Under such circumstances

INCORRECT		CORRECT
	I cannot work under this situation.		I cannot work under such circumstances.

You could say "I can't work in such a situation". You could also say "I can't work under such circumstance". The problem is using proper prepositions.

Under the table and Above board

INCORRECT		CORRECT
	He's so honest. He does all of his business on the table.		He's so honest. He does all his business above board.

The opposite of "under the table" is "above board". "On the table" only has a literal meaning as in "she cut the bread on the table".

Service our customers? or Provide service to our customers?

INCORRECT		CORRECT
	My responsibility is to service our customers.		My responsibility is to provide service to our customers.

It is awkward to say that someone "services another person". Maintenance people can service machines. When people service other people, "service" takes on a sexual meaning. To use "service" properly in the above sentence, use the verb "provide".

Bring back memories.

INCORRECT		CORRECT
	I hope the photographs I took will bring you a great memory.		I hope the photographs I took will bring back memories.

The word "bring" would suggest something has been physically given to you. "Bring back memories" is an exception and is a set phrase in English. However, "provide" can suggest that something enables you to get something else. You can also say "I hope the photographs I took will provide you with great memories".

Knock? or Knock on the door?

INCORRECT		CORRECT
	I didn't hear you knock on the door before you came in.		I didn't hear you knock before you came in.

"Knock on the door" is grammatically correct, but sounds awkward. "Knock" is the correct and natural word choice. "On the door" is understood in the context and is therefore redundant.

BC 323 or 323 BC?

INCORRECT		CORRECT
	Alexander the Great died in BC 323.		Alexander the Great died in 323 BC.

BC should follow the year. AD (Anno Domini, Latin for "In the Year of the Lord") can come before or after it. For example, 2008 AD and AD 2008 are both correct.

New coming juniors?

INCORRECT		CORRECT
	I want to welcome all the new coming juniors.		I want to welcome all the new students.

"New coming juniors" is the direct translation from Chinese original. The term "Juniors" is rarely used in English, especially in this context. "New students" is possibly the best term as it is sipmle and to the point.