Questions

Dull means not sharp, not shining, not bright, ...

Hence, the given words are all that means the opposite of dull.

Lee Falk

Multiple users can't share a local temporary table

The size of the pupil of the automatically adjusts itself according to the intensity of light passing through it; if the intensity is more, the size is less, if less, it is more. So in our case the pupil should dilate i.e , increase in size to be able to see in the dark. This switchover takes some time. But here the entry into the dark room is immediate. So the eye has no time to adjust itself and hence is not able to see at all for a while. 

Rafael Nadal defeated Daniil Medvedev in the men's singles title at the 2019 US Open. It was Nadal's 19th Grand Slam singles title, and fourth US Open title.

Every year on 18 April, ICOMOS (International Council on Monuments and Sites) celebrates the International Day for Monuments and Sites (also called as World Heritage day), whose establishment was approved by the 22nd UNESCO General Conference in 1983.