Difference beetween those two forms

[Tom]

English Language Proficiency Tests, Advanced Level

ESL/EFL Test #99 "The Parliamentary Candidate (2)", question 1

Henry: Hello.
Man's voice: Is that Mr. Henry Orpington, the parliamentary candidate?
Henry: Yes, ..........

(a) talking
(b) dictating
(c) speaking
(d) deciding

English Language Proficiency Tests, Advanced Level

ESL/EFL Test #99 "The Parliamentary Candidate (2)", answer 1

Henry: Hello.
Man's voice: Is that Mr. Henry Orpington, the parliamentary candidate?
Henry: Yes, speaking.

Correct answer: (c) speaking
_________________________

Hi!
What's the difference beetween those two forms?
Are they both correct?
When do we use them and which one is more popular or proper?

Thanks,
Tom

[Mister Micawber]

.
Which two forms? Only speaking is correct, among the choices given. It is a set phrase.

.
_________________
Canadian-American native speaker
who teaches English for a living at Mister Micawber's
ESL cafe: Interview with Mr. Micawber

[tommy]

Sorry, I wrote it by mistake.