What are the two active sites or domains on a repressor protein?

DNA binding domain and allosteric domain

Explanation:

Repressors are proteins that inhibit gene expression, They usually have DNA or RNA binding site which enables them to binde to the operator or associated silencers. Allosteric domain is the site for the binding of other molecules, such as  corepressors and inducers that regulate repressor's activity.

the answer is a or when it says crossing over

lizards have adapted to life in the desert. some desert lizards have toes with spiny scales to them run across the sand without sinking. some use the sand to hide from predators, or to search for small animals that they prey upon.