Accumulation of which acid in muscle fibres leads to cramps in muscles?

Identify the correct combination of $A$, $B$, and $C$ involved in lactic acid fermentation.
$C_6H_{12}O_6 \rightarrow A + B \rightarrow$ Lactic acid + $C$

The enzyme involved in alcoholic fermentation is .........

Fermentation is performed by:

When yeast ferments glucose, the products obtained are

Fermentation is a/an ...... process.