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.

Passage: The City of Charleston Fire Department consists over 300 full-time firefighters. These firefighters operate out of 19 companies located throughout the city: 16 engine companies, two tower companies, and one ladder company. Training, Fire Marshall, Operations, and Administration are the divisions of the department. The department operates on a 24/48 schedule and had a Class 1 ISO rating until late 2008, when ISO officially lowered it to Class 3. Russell (Rusty) Thomas served as Fire Chief until June 2008, and was succeeded by Chief Thomas Carr in November 2008.
How many companies aren't there in the City of Charleston Fire Department?

Passage: All equipment must be suitable for a mixed-gender force. Combat helmets, rucksacks, combat boots, and flak jackets are designed to ensure women have the same level of protection and comfort as their male colleagues. The women's uniform is similar in design to the men's uniform, but conforms to the female figure, and is functional and practical. Women are also provided with an annual financial entitlement for the purchase of brassiere undergarments.
What is a requirement for equipment for the CE?

Passage: On 15 September 1940, known as the Battle of Britain Day, an RAF pilot, Ray Holmes of No. 504 Squadron RAF rammed a German bomber he believed was going to bomb the Palace. Holmes had run out of ammunition and made the quick decision to ram it. Holmes bailed out. Both aircraft crashed. In fact the Dornier Do 17 bomber was empty. It had already been damaged, two of its crew had been killed and the remainder bailed out. Its pilot, Feldwebel Robert Zehbe, landed, only to die later of wounds suffered during the attack. During the Dornier's descent, it somehow unloaded its bombs, one of which hit the Palace. It then crashed into the forecourt of London Victoria station. The bomber's engine was later exhibited at the Imperial War Museum in London. The British pilot became a King's Messenger after the war, and died at the age of 90 in 2005.

What is the date of the celebration of Britain Day?