Enzymes are sensitive to .....

Enzymes are proteins. Proteins are long chains of amino acids linked to each other by peptide bonds. Amino acids have many functional groups in their structure. Many of these functional groups are ionisable. As they are weak acids and bases in chemical nature,this ionisation is influenced by the $pH$ of the solution. For many enzymes,activity is influenced by the surrounding $pH$. This is depicted in the curve below. Explain briefly.

The given graphical representation relates to enzyme activity under three conditions ($pH$,temperature,and substrate concentration). What do the given axes $X$ and $Y$ represent?
$X$-axis $-$ $Y$-axis

Select the incorrect statement regarding the given graph.

According to the generally accepted rule,the rate of reaction doubles or halves for every $.........^{\circ}C$ change in temperature.

Match the following Column-$I$ with Column-$II$ and select the correct option.

Column-$I$	Column-$II$
$(A)$ Transferases	$(i)$ $H_4P_2O_7$ related reactions
$(B)$ Lyases	$(ii)$ Hexokinase
$(C)$ Isomerases	$(iii)$ Cytochrome oxidase
$(D)$ Ligases	$(iv)$ Aldolase
$(E)$ Oxidoreductases	$(v)$ Glucose-$6$-phosphate $\rightarrow$ Fructose-$6$-phosphate