Questions

Ionic character depends on the electronegativity difference between the bonding elements. The greatest the elctronegativity diffference the greatest the ionic character.

Here in the given options, H-F has has the greatest ionic character. The electronegativity of Hydrogen is 2.1 and that of Fluorine is 4. Now the electronegativity difference is 4 - 2.1 = 1.9.

The size of the pupil of the eye 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 sometime. 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.

Lewis Edson Waterman patented the first practical fountain pen in 1884.

Jupiter    63

Saturn    60

Uranus   27

Neptune 13

Pluto       3

Mars       2

Earth       1

Venus     0

Mercury   0

As clear from the diagram, AD2=122+92=152

 So, AD = 15