Akono lists some of the variables in his investigation to answer the question: How does the mass of salt affect the speed of rusting? Variables:
- amount of salt
- how much of the nail has gone rusty?
- type of nail
- time nail is left in test tube
--From the list of variables above, identify the variable Akono should change.

Amount of salt

Explanation:

Since he is testing the speed of rusting depending on the mass of salt, the variable he should change in the experiment is the amount of salt.

The type of nail and the time the nail is left in the test tube should not change in order to keep the experiment fair. How much of the nail has gone rusty is a dependent variable and depends on the amount of salt.

- calcium has greater affinity to bond with electron receptors than hydrogen does and hence, it has the ability to replace hydrogen in most of its compounds.

- lithium has 2 valence electrons in the product because it can make only 1 bond with hydrogen. beryllium has 4 valence electrons in the product because it can only make 2 bonds. it has fewer electrons than neon and can react with electron donors. each hydrogen has 2 valence electrons, the same as helium.

- the covalent bond formed between carbon and hydrogen is polar because carbon is more electronegative than hydrogen and it attracts the bonded electron pair closer to itself, thus giving hydrogen a partial positive charge.

- a hydrogen bond is a relatively weak bond that hydrogen atoms make with the electronegative atoms nitrogen, oxygen or fluorine.

so the best choice is a.) 2 calcium (ca) atoms