How to calculate natural abandunces

Let x equal the percentage abundance of one of the two isotopes. The other isotope must then have an abundance of 100 percent minus x percent, which you express in decimal form as (1 - x). For nitrogen, you can set x equal to the abundance of N14 and (1 - x) as the abundance of N15.

Explanation:

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.

the answer is na (sodium)