This cold river of air travels from west to east in the northern hemisphere. In winter, it dips south helping to bring cooler air to most parts of the United States. This is the jet stream.

Polar Jet stream

Explanation:

Polar Jet stream is also called the polar front jet or mid latitude jet steam, it is a very powerful belt of the upper level winds which sits above the polar front. It is the strongest wind in the tropopause, it's movement is towards the westerly direction of the mid latitude.

- 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

i think that the answer is c