"His boss has always barked at the staff."
Translation:Son chef a toujours aboyé sur le personnel.
"Aux personnel" is what I was corrected to! Why is "au personnel" wrong if the word "staff" is supposed to be grammatically singular in both English and French?
Shouldn't "Son chef a toujours aboyé après le personnel" or "Son chef a toujours aboyé contre le personnel" be accepted as well? Or are there differences in meaning to "aboyer sur qn."?
It is idiomatic in French to say "aboyer sur qqch" (to bark at something), but one could also say "aboyer après" or "aboyer à".
shouldn't "...has always barked..." require the use of the imparfait tense instead of the passé composé?
No, the imparfait, while conveying an unspecified length of time, refers to the past. The passé composé serves as both the past perfective AND the perfect, and it's the perfect that is meant here. If you are unaware of the grammatical term "perfect", it refers to actions beginning in the past that continue to affect the present, which is what they mean by "has always barked" (he has barked before and continues to bark now).