Which classification system is used in most of the world's prominent herbaria?

How are the treatises prepared by $Bentham$ and $Hooker$ useful in the field of botany?

$S$ Statement: Periodic poisoning is done to protect against fungi,insects,and moisture.
$R$ Reason: To preserve dried plant specimens,they are sprayed with specific chemicals; this process is called poisoning.
$(a)$ Both $S$ and $R$ are true,and $R$ is the correct explanation of $S$.
$(b)$ Both $S$ and $R$ are true,but $R$ is not the correct explanation of $S$.
$(c)$ $S$ is true and $R$ is false.
$(d)$ $S$ is false and $R$ is true.

Where are maps and botanical books collected and stored?

How are insects preserved in an insect museum?

Where is the label placed on a herbarium sheet?