In the $lac$ operon, what does the term "$lac$" refer to?

The one gene-one enzyme hypothesis was postulated by

Identify the $INCORRECT$ statement with reference to the regulation of gene expression.

Two scientists were awarded the Nobel Prize in $2006$ for $RNA$ interference. On which organism did these scientists discover this mechanism?

Statement $I$: Lac operator is present only in $lac$-operon and it interacts specifically with $lac$-repressor only.
Statement $II$: Each operon does not have a specific operator and a specific repressor.

The 'Operon model' for gene regulation in bacteria was proposed by: