You have a blind spot in each eye where the optic nerve connects to the retina.
Why it is true
Because there are no light-sensitive cells in this exact spot, your brain automatically fills in the missing information based on the surrounding image.
Source: Ophthalmology
Would you rather be asked first?
This is the reading side of the site, so the answer is in the sentence above — that is the whole point of it. Test yourself works the other way round: the question comes on its own, and the fact and the explanation only appear once you have answered.