In this diagram of the process of DNA replication at a replication fork, the strand labeled B is the:

A template strand

B lagging strand

C leading strand

The leading strand is the newly synthesized DNA with addition of nucleotides moving in the same direction as the replication fork. Since DNA replication is 5' to 3', this means that the leading strand will always have its 3' end towards the replication fork.

D Okazaki fragment

E RNA primer