helm本是舵柄，這裡是指操舵者，也就是當權者或領導人(to be in command or in charge; to be the leader)
例如﹕
After the election, one of the candidates will be at the helm of the U.S.
選舉後，後選人之一就成為美國領袖。
Mr. Ma, the leader of Taiwan, has been at the helm for almost four years.
台灣領導人馬先生，執政將近四年。
Because of different personalities, not everyone can be at the wheel.
由於性格不同，不是每個人都能帶頭。
(to be at the helm = to be at the wheel)
to be at large﹕
自由自在，逍遙法外，多指未被逮捕的犯人(to be free or unconfined, generally refer to a criminal before arrest)
例如﹕
Police report that the murderer is still at large.
警察宣佈謀殺兇手仍在逍遙法外。
With lack of law enforcement, many escaped criminals have been at large.
由於警力短缺，許多逃犯還在逍遙法外。
但也指「蔓延」或「通常」。例如﹕
During the season, the flu virus has been at large for weeks.
在這季節裡，感冒病毒已蔓延數周。
Many people in the world at large are peace-loving.
世上許多人通常都是愛好和平。
(at large = in general)
to be at loggerheads (with someone)﹕
loggerhead 本意是笨蛋，傻瓜。這裡指不和或相爭。
(in the state of a quarrel or dispute)
例如﹕
If you walk (a mile)in his shoes, you would not be at loggerhead with him.
假如你處於他的立場，你就不會與他爭吵。
(to walk in someone's shoes是處於某人的境地； a mile只是加強語氣，可以省去)
For more than 60 years, the U.S. has been at loggerheads with China on the Taiwan issue.
60多年來中美兩國由於台灣問題而不和。
It is sad that many Chinese tend to be at loggerheads with their fellow Chinese.
令人遺憾的是許多老中常與自己同胞相鬥。
(tend後接不定詞，是易於；往往會)
If some Chinese politicians had not been at loggerheads with one another, China could have become a superpower.
如果一些老中政客沒有彼此相鬥，中國可能老早成為超強大國。
(就是與過去事實相反的假設語態)
To be at a loss (to do something)﹕
指困惑不解，不知所措 (unable to decide or to be puzzled)
例如﹕
Under so much pressure, Mr. B is (was) at a loss as to what to do next.
B先生在很多壓力下，不知下一步如何處理。
Should I win the lottery, I would be at a (complete) loss on how to spend the money.
假如我贏了彩券，我真不知如何花費。
(complete只是加強語氣)
At the first date with his girlfriend, Mr. A was at a loss for words.
A先生第一次與女友約會時，找不出話說。
(at a loss for words = one does not know what to say)
She has been at a loss to understand what Mr. A intended to do.
她很困惑不解A先生有何企圖。
to be at the top of the ladder (或tree)﹕
指登上高位，非常成功(to be in high position; to be successful)
例如﹕
With hardwork and perseverance, Mr. B is now at the top of the ladder in his business.
B先生工作努力，鍥而不捨，現在生意十分成功。
In the field of software engineering, Bob has been at the top of the tree.
在軟體工程領域，Bob已經登上高位。
You can be at the top of the ladder if you put your mind to it.
假如你專心認真工作，你就可以處於高位。
反之，at the bottom of the ladder (或tree)
就是處於低層位子。例如﹕
Because of language barrier, many Chinese immigrants have to work at the bottom of the tree.
由於語言障礙，許多老中移民必須從事低層工作。
to be at one's wits' (或wit's)end﹕
wit 本意是風趣或智力。這是指困惑的，費解的，或是智窮計盡，不知所措(to be confused, puzzled or perplexed)
例如﹕
We are all at our wit's end about this touchy problem.
我們對這敏感問題，感到束手無策。
(下期待續)
