Question about telephone English

[sula54]

Dear everyone,

Please have a look of this question:

May I speak to Miss Dolly?
(A) I'm Miss Dolly.
(B) She's speaking.
(C) Here's Miss Dolly.
(D) Hi, it's me.

In the book the correct answer is (B).

According to Michael Swan's book "Practical English Usage" p.554:
telephoning
3. saying who you are
Hello, this is Corinne. (NOT USUALLY...I'm Corinne)
'Could I speak to Jane Horrabin?' 'Speaking' (OR This is Jane
Horrabin (speaking).) (US This is she.)

(A) is not right.=> should be "This is Miss Dolly."
(C) is not right.=> should be "This is Miss Dolly."
(D) is not right.=> should be "This is Miss Dolly."

But how about (B)? To the best of my knowledge, I can't think of any example people will answer like "He's speaking." or "She's speaking."

Also, for the fourth choice, can I base on the answer of "This is she." to form the other answer "It's she."? And I wonder it's alright if I give an answer of "That's me" to the question.

Thank you in advance.

[Casiopea]

May I speak to Miss Dolly?
(A) I'm Miss Dolly.
(B) She's speaking.
(C) Here's Miss Dolly.
(D) Hi, it's me.

All of them are used by native speakers, but (B) is the correct choice in terms of formal usage. It's the long form for "Speaking".

Hello, this is Corinne. (NOT USUALLY...I'm Corinne)

In other words, "I'm . . . " isn't the usual response, but it is used.

'Could I speak to Jane Horrabin?' 'Speaking' (OR This is Jane
Horrabin (speaking).) (US This is she.)

"Speaking" is also short for "She's speaking" or "I'm speaking".

I can't think of any example people will answer like "He's speaking." or "She's speaking."

But they are indeed used by native speakers all the time. It's synonymous with, "The person you are looking for is speaking." In other words, "the person" is a singular noun, its pronoun is "she" or "he", which gives, e.g., "She's speaking."