Active sites in enzymes are where substrates bind. Once they bind, a catalytic reaction occurs as a complex between substrate and enzyme is formed. Enzymes are termed as biocatalysts or simply catalysts since they speed up the catalytic reaction. After the reaction, they simply revert back to their original form, after having adjusted to fit with substrate.
"The Solar electricity source of energy comes from the sun’s rays. It is more often in the form of a panel known as the solar panel. It has a photovoltaic system that generates and supplies energy in commercial and residential areas. Even though numerous countries are using this type of electricity to save electric-induced power, it is not used for a number of reasons. One is that 1 panel with a size of 6 by 10 solar cells is expensive. There are countries who cannot afford to buy them. Two, it requires a larger area to place the panel. Three, the efficiency is low. The smaller the panel is, the lower its efficiency and therefore produces lesser power to generate a specific area."
It looks like the answer would be D