Many plants, such as the potato plant, avoid insect predation by producing highly toxic sap. however, the potato bug, unlike most insects, has adapted to the toxins and can still eat the potato plant. in turn, over a long period of time, potatoes are likely to develop more chemical defenses against the potato bugs. this type of consistent adaptation between two species is known as

An adaptation can be defined as the changes that occur in the body of the organism which allows it survive in the surrounding changing environment. The physiological adaptation is the adaptation in which the internal systematic responses that an organism produce against an external stimuli in order to sustain it's life.

The given situation is an example of physiological adaptation because potato plant will produce toxic sap in response to external stimuli bugs, the bugs later on attains adaptation to resist the effects of toxic sap.

- 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

let that person have a turn to speak : )