Questions

Direct method,

 Subtraction method,

 Modulo-Division method,

 Digit-Extraction method,

 Mid-Square method,

 Folding method,

Pseudo-random method

Here given that 9 = 63, 8 = 48, 7=35, ... 

The given question follows a pattern that

9 x (9 - 2) = 9 x 7 = 63

8 x (8 - 2) = 8 x 6 = 48

7 x (7 - 2) = 7 x 5 = 35

Similarly, 4 x (4 - 2) = 4 x 2 = 8.

Magnesium is dissolved in seawater at a concentration of about 1,000 parts per million and is the only metal directly extracted from seawater.

Electronegativity is the tendency for an atom to attract electrons. There are general trends on the periodic table which you can use to determine the relative electronegativity for different elements, but otherwise you can also look at their valence shell and effective nuclear charge to determine their relative electronegativity.

Here from the given options, Lithium has least tendency to attract electrons and thus has a lower electronegativity.

Acid Precipitation or Acid rain is caused by a mix of Sulfur Dioxide, Carbon Dioxide, Nitrogen Oxides.

A Chemical reaction that begins when compounds like sulfur dioxide and nitrogen oxides are released into the air. These substances can rise very high into the atmosphere, where they mix and react with water, oxygen, and other chemicals to form more acidic pollutants, known as Acid Rains.

A traffic light.

It has three 'eyes' (the red, orange and green lights) and the leg is the pole holding it up. Many people beg the light to stay green as they’re approaching.