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 best, worst and average case complexity refer to three different ways of measuring the time complexity (or any other complexity measure) of different inputs of the same size. Since some inputs of size n may be faster to solve than others, we define the following complexities:
answer:
What are the three secondary expressions used to represent case complexity? 


question:
Passage: Extension causes the rock units as a whole to become longer and thinner. This is primarily accomplished through normal faulting and through the ductile stretching and thinning. Normal faults drop rock units that are higher below those that are lower. This typically results in younger units being placed below older units. Stretching of units can result in their thinning; in fact, there is a location within the Maria Fold and Thrust Belt in which the entire sedimentary sequence of the Grand Canyon can be seen over a length of less than a meter. Rocks at the depth to be ductilely stretched are often also metamorphosed. These stretched rocks can also pinch into lenses, known as boudins, after the French word for "sausage", because of their visual similarity.
answer:
What is another word for thinning rocks in French?


question:
Passage: During Victoria's first pregnancy in 1840, in the first few months of the marriage, 18-year-old Edward Oxford attempted to assassinate her while she was riding in a carriage with Prince Albert on her way to visit her mother. Oxford fired twice, but either both bullets missed or, as he later claimed, the guns had no shot. He was tried for high treason and found guilty, but was acquitted on the grounds of insanity. In the immediate aftermath of the attack, Victoria's popularity soared, mitigating residual discontent over the Hastings affair and the bedchamber crisis. Her daughter, also named Victoria, was born on 21 November 1840. The Queen hated being pregnant, viewed breast-feeding with disgust, and thought newborn babies were ugly. Nevertheless, over the following seventeen years, she and Albert had a further eight children: Albert Edward, Prince of Wales (b. 1841), Alice (b. 1843), Alfred (b. 1844), Helena (b. 1846), Louise (b. 1848), Arthur (b. 1850), Leopold (b. 1853) and Beatrice (b. 1857).
answer:

What year was Queen Victorias last pregnancy?