What is the definition of Aperture

Ablind girl lost her pencil, book and what did she lose first? (this is really good for people who don't have an adequate amount of points! )

Acurator decides to display an eighteenth-century painting in a windowless room with controlled temperature and humidity. pick the answer that best describes the reasons for her choice: (1 point) 1)the curator wants to make sure that the temperature and humidity are comfortable for visitors. 2)keeping the temperature and humidity at a set level will save money. 3)the ultraviolet rays will damage the painting by fading and flaking the paint. 4)ultraviolet rays will fade the paint pigment and high temperature and humidity will damage the paint.

Which accidental cancels all other accidentals?