The 2 written in this formula (2 CH4 is a)

Answer : 2 represent the coefficient.

Explanation :

As we know that:

The coefficients used in the chemical equations shows that the relative amounts of each substance present and this amount can represent either the relative number of molecules or number of moles.

If there is no coefficient then one (1) is assumed.

That means,

The coefficient tell us about that how many molecules or atoms present in the chemical equation.

By the stoichiometry we have to convert moles of a reactant to moles of a product.

The given formula is:

In this formula, 2 represent the coefficient and 4 represent the subscript and C and H represents the symbol of element.

Hence, 2 represent the coefficient.

the best answer is d because the strong cohesion is caused by the ability of water molecules to undergo hydrogen bonding.

a is incorrect because when water solidifies, it becomes   ice, which expands and occupies a bigger volume for the same mass of water in its liquid state.

b is incorrect because water has high surface tension. besides bonding to itself it hydrogen bonds to other molecules at the top decreasing possibility for breaking of attractive forces.

c is incorrect because the water molecule has oxygen which is highly electronegative and so pulls the electron pair towards itself creating a dipole moment, making the molecule polar.

e is incorrect because water has strong adhesion, ability to stick to other molecules such as glass because of this molecules having stronger hydrogen bonding than water.