Questions

In the form of vinegar, acetic acid is known from very early times. It is got by oxidation of fermented liquors (10-15%, alcohol) by air under the influence of a bacteria called 'mycoderma acetic'

The resistance of metallic conductors e.g, platinum, increases with rise of  temperature . The increase in temperature results in a decrease of current which can be recorded in a galvanometer if the conductor is included in an electrical circuit. Thus the temperature can be known; platinum resistance thermometer is used generally for accurate scientific work. When two dissimilar metals are joined at the ends, and these ends are subjected to a difference of temperature, a current flows through the metals. Greater the difference of temperature , greater the current. So the curent strength can form the basis for measuring the difference in temperature. And when one of these temperatures is known, we can calculate the other.

90 D in RA means 90 Degrees in Right Angle. It is a logic question which is to be eloborated.

Some more of its kind are:

1. 52 W in a Y     -    52 Weeks in a Year

2. 7 C in a R        -    7 Colours in a Rainbow

3. 9 P in SS

4. 5 C in an OF

5. 12 S of the Z

A tetrad is best described by Four chromatids. It is formed from two homologous chromosomes, each consisting of two chromatids in the first stage of meiosis called prophase1.