choose? 8

[nado92]

I--------to spend the summer holiday in Alexandria when my sister suddenly fell ill.
a) had been planning b) have been planning
c) had planned d) have planned
It is a question from my test.

[Barb_D]

Nado, what is the first question we always ask you?

What is YOUR choice?

(However, I can see two possible answers to this. I'll be interested to see whether people agree that two of them can work, even though one is more natural to me.)

[nado92]

sure I remember . My answer was had been planning. But I don't have a reason.
Sorry it was a silly exam.

[EnglishMuffin]

(Now that Nado has answered)

Yes Barb I agree: A and C are both possible with A being the most frequently used. I hope they didn't mark C as wrong though.

[Barb_D]

What is the order of events? Is the planning still going on? If the answer to the second one is yes, then you want a form with "have." If the answer to the second is no, you want a form with "had."

[nado92]

thank you so much my good teachers.

[Raymott]

(Now that Nado has answered)

Yes Barb I agree: A and C are both possible with A being the most frequently used. I hope they didn't mark C as wrong though.

I'd mark C wrong - if only because A is obviously a better choice, and that's the premise of multichoice exams.
In any case, C doesn't work for me.
It would be alright as "I had planned to spend the summer holiday in Alexandria but my sister suddenly fell ill." or maybe, "I had already planned to spend the summer holiday in Alexandria when my sister suddenly fell ill."

But the exact wording really requires A. It's a tense sequence test: An action in the past perfect continuous is interrupted by an event expressed in the simple past.