When considering the semi-conservative model of DNA replication, how many of the resulting DNA molecules would have a piece of the original DNA molecule after two replication events?
A. 1
B. 2
C. 3
D. 4
URGENT PLEASE HELP

Lactase is essential for digesting lactose in milk. this enzyme is specific for this sugar. why? molecules and active sites vary in size; only properly sized molecules can fit.there is a precise compatibility between the active site and the lactose molecule.specificity refers to the action of the enzyme, such as hydrolysis, and relatively few molecules can be hydrolyzed.reaction-specific enzymes assume a fit by folding around the most numerous substrate molecules.