instruction:
This task is about creating an unanswerable question based on a given passage. Construct a question that looks relevant to the given context but is unanswerable. Following are a few suggestions about how to create unanswerable questions:
(i) create questions which require satisfying a constraint that is not mentioned in the passage
(ii) create questions which require information beyond what is provided in the passage in order to answer
(iii) replace an existing entity, number, date mentioned in the passage with other entity, number, date and use it in the question
(iv) create a question which is answerable from the passage and then replace one or two words by their antonyms or insert/remove negation words to make it unanswerable.
question:
Passage: The effects of local surface low pressure are extremely limited because upper-level subsidence still continues to block any form of air ascent. Also, to be protected against rain-bearing weather systems by the atmospheric circulation itself, the desert is made even drier by his geographical configuration and location. Indeed, the extreme aridity of the Sahara can't be only explained by the subtropical high pressure. The Atlas Mountains, found in Algeria, Morocco and Tunisia also help to enhance the aridity of the northern part of the desert. These major mountain ranges act as a barrier causing a strong rain shadow effect on the leeward side by dropping much of the humidity brought by atmospheric disturbances along the polar front which affects the surrounding Mediterranean climates.
answer:
what is blocked buy the surface low pressure?


question:
Passage: The other Ancient Greek dialects, Ionic, Doric, Aeolic, and Arcadocypriot, likely had the same three-way distinction at one point, but Doric seems to have had a fricative in place of /tʰ/ in the Classical period, and the Ionic and Aeolic dialects sometimes lost aspiration (psilosis).
answer:
What ancient dialects had the same two-way distinction at one point?


question:
Passage: However, according to research firm NPD, sales of devices running Windows in the United States have declined 21 percent compared to the same time period in 2011. As the holiday shopping season wrapped up, Windows 8 sales continued to lag, even as Apple reported brisk sales. The market research firm IDC reported an overall drop in PC sales for the quarter, and said the drop may have been partly due to consumer reluctance to embrace the new features of the OS and poor support from OEM for these features. This capped the first year of declining PC sales to the Asia Pacific region, as consumers bought more mobile devices than Windows PCs.
answer:

What is ICD?