What's the meaning of "knowing one's onions"?

English Language Tests, Intermediate level

ESL/EFL Test #384 [color=blue]“English Slang Idioms (115)”, question 2

“Jake is a good employee. That guy sure knows his . There isn’t anything about how this place is ran that he doesn’t know about,” Marcie told Melissa.

(a) onions
(b) ideas
© feelings
(d) shoes

English Language Tests, Intermediate level

ESL/EFL Test #384 [color=blue]“English Slang Idioms (115)”, answer 2

“Jake is a good employee. That guy sure knows his onions. There isn’t anything about how this place is ran that he doesn’t know about,” Marcie told Melissa.

Correct answer: (a) onions

Your answer was: [color=green]correct
[size=200]_________________________[/size]

What’s the meaning of “knowing one’s onions”?

.
Be knowledgeable.
.

Hi,

I believe there is a grammatical error in this text-"about how this place is ran “.
Shouldn’t we say " this place is run’ ?
If it is actually a mistake, there is another one in question no.3 " things are ran”.

Hello Zishuli,

You are right. The past participle of the irregular verb “run” is “run”. The use of “ran” as a past participle would be marked as wrong in any reputable grammar test.

In the passive voice, the verb “run” should use a form of the verb “be” and the past participle (“run”). For example:
[i]- I know only too well how this place is run.

  • Three different simulations were run.[/i]

You would also use the past participle (“run”) to build the perfect tenses:
- We have already run three different simulations.

The word “ran” is used for the simple past tense, active voice:
[i]- He ran the place with an iron hand.

  • We ran three different simulations.[/i]

Nearly all men can stand adversity, but if you want to test a man’s character, give him power.
— Abraham Lincoln

Hi Zishuli,

Thanks a lot for spotting this typo which we’ll correct tomorrow.

Regards,
Torsten[YSaerTTEW443543]

TOEIC listening, photographs: Daydreaming[YSaerTTEW443543]