2. Messages move to and from the brain along thin cells called?

Messages to and from the brain travel along the nerves, which are strings of long, thin cells called neurons.

Explanation:

Messages to and from the brain travel along the nerves, which are strings of long, thin cells called neurons (see Figure 6.2). Chemical- electrical signals travel down the neurons much as flame travels along a firecracker fuse. ... Dendrites receive impulses, or messages, from other neurons and send them to the cell body.

it has one origin of replication, but it proceeds in two directions - d)

the answer is c) an oak tree