Answer:
A
Explanation:
that should be the answer
<u>Answer:</u> The correct option is
<u>Explanation:</u>
A catalyst is defined as the chemical species that increases the reaction rate but does not participate in it and is left behind after the completion.
A homogeneous catalyst is one that is present in the same phase as the reactants and products.
A heterogeneous catalyst is one that is present in different phase as that of reactants and products.
For the given chemical reaction:

As all the reactants and products are in gaseous state so, the homogeneous catalyst must also be in the gaseous state only.
Hence, the correct option is 
Metal usually donates electrons. The concept behind this phenomenon is stability. The elements with the most stable electronic configuration are the noble gases in Group 5A. As a result, the other elements donate or accept electrons so that they would be like the noble gases. Since metals are past their nearest noble gas element, they have to shed their electrons. When they do, they become cations which are positively charged ions.
Scientific would be the word to fill in the blank
D.
The main properties of water are its polarity, cohesion, adhesion, surface tension, high specific heat, and evaporative cooling.