What is difference between present perfect and present perfect continuous?

Question

I've been studying English by the book "English Grammar in Use" for a month. There is a Unit about present perfect and - continuous, also Exercises.

Please check the below exercises...

A. You meet a woman who tells you that she teaches English. You ask her: (how long/ teach / English?)

B. You are talking to a friend about Joe. Joe now works at the airport. You ask your friend: (how long / work / at the airport?)

According to the keys exercises on the book, we can use either usages 'present perfect and present perfect continuous'.

But there is other case,

C. You have just arrived to meet a friend. She is waiting for you. You ask: (wait / long)

the key says the answer is present perfect continuous.

My book says, usually to express 'how long' we use present perfect continuous. I can understand about that. But we can use also continuous for Exercise A and B. I can't understand why I can use that even though they say about 'How long'. If it is not too important, why should(or must) I use 'present perfect' for Exercise C?

summary,

what is really different point between 'present perfect' and 'present perfect continuous'?

Answer 1

Q: What is really different point between 'present perfect' and 'present perfect continuous'?

Look at the subtle difference between these two statements:

Karen has been sitting at the airport for two hours. (Pres. Perfect Cont.) Karen has sat at the airport for two hours three times before.(Pres. Perf.)

What's the difference?

A: Present Perfect Continuous is used when an action or multiple actions started in the past and continue in the present, or actions just finished, and there is an interest in the result.

The formula:

[Subject] + [has/have been] + [base verb, plus an "ing" suffix]

Tom has been working [at McDonald's for two weeks.] Helen has been singing, laughing,and watching [TV all day.] I have been studying [Mongolian for 8 years now.]

Present Perfect: is used to show an action has taken place once or many times before now. The difference is subtle, so use the formula listed for both. Use present perfect for something that happened at some point before now, and the person, place, or thing it happened to is still living or existing in the present right now. (Ref: Purdue University, Purdue Writing Lab (https://owl.purdue.edu)

The formula:

[Subject]    +     [has/have]       +     base verb (past tense)

 The tractor   has              been broke  [for over two days.]
    Larry      has              walked  [to California before.]
     I         have             bicycled  [to Canada three times.]

I hope this answers your question.

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More examples of Present Perfect Continuous sentences:

Examples: 1. This plane has been sitting on the runway for over an hour.

(the action of the plane sitting on the runway started over one hour ago in the past, and continues into the present when the speaker utters it.) Present Perfect Continuous Affirmative.

          2. John hasn't been walking to work for over a month.

(the action of John not walking to work started over a month ago and continues into the present.) Present Perfect Continuous Negative

          3. Has the tractor been running all this time?

(the action of the tractor in operation (running) started in the past and continues in the present) Present Perfect Continuous Interrogative (Question)

         4. Hasn't this movie been playing at the theater too long?

(the action of the movie playing at the theater started in the past too long ago and continues to be played in the present at the theater) Interrogative negative (asking the question negatively [hasn't])

*Within Present Perfect Continuous: There are Affirmative, Negative, Interrogative, and Interrogative negative.