Questions

Oenology is the science and study of wine and winemaking. So person who is specialist in that is called as Oenologist.

An ignition safety switch is a safety device can shut off the engine if the operator falls off the PWC or out of the powerboat, or is otherwise thrown from the proper operating position.

How it works:

It allows the engine of the vehicle to shut off or to be turned off immediately as it is to prevent further complications to happen as this is being used when an emergency is launched

Where it is used:

Most powerboats and PWCs come equipped by the manufacturer with an emergency engine cut-off switch.

Water can moderate temperature because of the two properties: high-specific heat and the high heat of vaporization. 

Hence, all the above given options are not the properties of water.

Apostrophe(‘) symbol is used before a number to make it a text or label.

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.