Energy. A solute can only move against concentration gradients using active transport which requires energy
I could be wrong I’m not very smart but I think it’s b
During DNA Replication, the DNA molecule unzips itself so that there are two free strands of DNA. Both of those strands then create new complementary strands of DNA. Thus every subsequent generation of DNA uses one of the parent cell's strand of DNA as a template, which is why DNA replication is said to be semi-conservative. Hope this helped!
