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: Zinc metal is produced using extractive metallurgy. After grinding the ore, froth flotation, which selectively separates minerals from gangue by taking advantage of differences in their hydrophobicity, is used to get an ore concentrate. This concentrate consists of about 50% zinc with the rest being sulfur (32%), iron (13%), and SiO
2 (5%). The composition of this is normally zinc sulfide (80% to 85%), iron sulfide (7.0% to 12%), lead sulfide (3.0% to 5.0%) silica (2.5% to 3.5%), and cadmium sulfide (0.35% to 0.41%).
What is used to eliminate the metal zinc?

Passage: The control of associated biodiversity is one of the great agricultural challenges that farmers face. On monoculture farms, the approach is generally to eradicate associated diversity using a suite of biologically destructive pesticides, mechanized tools and transgenic engineering techniques, then to rotate crops. Although some polyculture farmers use the same techniques, they also employ integrated pest management strategies as well as strategies that are more labor-intensive, but generally less dependent on capital, biotechnology and energy.
What is one of the great polyculture challenges that farmers face?

Passage: The school has many nationally and internationally acclaimed scholars in social security, health care, health disparities, communication, social and health policy, and individual and family development. Many of the faculty have training in both social work and public health. The school's current dean is Edward F. Lawlor. In addition to affiliation with the university-wide Institute of Public Health, Brown houses 12 research centers. The Brown School Library collects materials on many topics, with specific emphasis on: children, youth, and families; gerontology; health; mental health; social and economic development; family therapy; and management. The library maintains subscriptions to over 450 academic journals.

How many academic journal subscriptions does the Brown School Library have for mental health issues?