In an automobile's catalytic converter,
several reactions occur to reduce the amount
of carbon monoxide, nitrogen monoxide, and
unburned hydrocarbon pollutants that are
released in the exhaust gases. the exhaust
gases pass over a ceramic honeycombed
structure with a large surface area plated with
the catalysts platinum, rhodium, and
palladium before they leave the tail-pipe. in
spite of these safeguards, however, studies
have shown that most of the pollutants
released from a car happen during the first
one to two minutes after the car is started,
and then decrease significantly after that.
which factor affecting reaction rates is
responsible for this phenomenon?
a presence of a catalyst
b temperature
c concentration of reactants
d surface area

The most of the pollutants (carbon monoxide, nitrogen monoxide and unburned hydrocarbons) are released from the car during the first one to two minutes after the car is started, and then decrease significantly after that, due to increasing the temperature which supply the system by heat that required to oxidize the released gases by increasing the rate of the chemical reaction.

Then, the correct answer is the temperature  (B).

- 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