A project manager is building a project network that involves testing a prototype. She must design the prototype $($activity $1),$ build the prototype $($activity $2),$ and test the prototype $($activity $3).$ Activity $1$ is the predecessor for activity $2$ and activity $2$ is the predecessor for activity $3.$ If the prototype fails testing, she must redesign the prototype; therefore, activity $3$ is a predecessor for activity $1.$ This is an example of

a$.$

Conditional statements.

b$.$

Looping.

c$.$

Having more than one start node.

d$.$

Good network development.

e$.$

Natural network flow.