Meaning of overhear

[Condoliza]

Business English Courses, Elementary Level

ESL/EFL Test #67 "Business dialogue on the phone", question 10

Bill: I couldn't help but ......... you're having chicken for dinner tonight. Can I come over?

(a) overhear
(b) eavesdrop
(c) listen
(d) comprehend

Business English Courses, Elementary Level

ESL/EFL Test #67 "Business dialogue on the phone", answer 10

Bill: I couldn't help but overhear you're having chicken for dinner tonight. Can I come over?

Correct answer: (a) overhear
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what does the word overhear mean?

Condoliza

[Conchita]

'To overhear' means to hear accidentally (often what you are not meant to hear):

I overheard a conversation on the train.
The children overheard their parents talking about the surprise.

[Saneta]

why not overheard in that sentence?
thanks

[Duset]

Yes, why not overheard? It seems to be the past tense in that sentence.