Rainfall is measured by a precise instrument called as __________ .
A. Rain meter
B. Rain gauge
C. Rain tube
D. None of these

Hint:It is also known as udometer, pluviometer or an ombrometer.
They calculate the precipitation in millimetres in height obtained on each square meter during a certain interval, equivalent to litres per square metre. They are classified into three major types.

Complete answer:
Rainmeter is an unrestricted and open-source desktop customization utility for Windows, published under the GNU GPL v2 license. It enables users to establish and present user-generated customizable desktop widgets or applets called "skins" that exhibit evidence. This option is incorrect.
A rain gauge is a meteorological tool to calculate the precipitating rain in an allotted amount of time per unit area. The instrument comprises a collection container which is positioned in an open area. It is actually just a cylinder that detects rain. If an inch is received in the cylinder, it implies an inch of rain has fallen. Most standard rain gauges have a broad funnel directing into the cylinder and are calibrated so that one-tenth of an inch of rain estimates one inch when it is collected inside. This option is correct.
A rain tube cannot measure rainfall. This option is incorrect.
The option "none of these" is irrelevant. This option is incorrect.

Hence the correct answer is option B.

Note:The rain gauge was invented by Cheugugi in 1441, in Europe.
The rain gauge was invented in order to calculate rain amounts and to deduce much tax to charge each citizen. The National Oceanic and Atmospheric Association (NOAA) weather observer system, uses manual rain gauges with an 8 inch diameter. These are the most authentic and expensive rain gauges.