Position-time graphs assignment and quiz

I used the Jerold Touger book for my general physics class for several years. I don't use it anymore -- the writing was way too complicated for my students to read, though I appreciated some of the conceptual treatments and problems. I still use some Touger problems for homework.

Consider the position-time graph in red, representing the motion of a fish. Touger's problem asks a number of questions about average velocity and instantaneous velocity at various times. I assign the problem... and then I give a quiz based on the problem. I drew the five lines in black on the graph, and scanned this graph into the quiz. Here is the quiz, which is based almost verbatim on Touger's posed questions:

A marine biologist shooting video of a rare species of fish uses the video data to produce the graph of the fish’s position x plotted against clock reading t in the graph above.

Velocity is the slope of a position-time graph. For each question, indicate which line on the graph above you should take the slope of in order to answer the question. Mark your choice as:
(A) Line #1
(B) Line #2
(C) Line #3
(D) Line #4
(E) Line #5

1.What is the fish’s average velocity between t = 0 and t = 8 s?

2.What is the fish’s average velocity between t = 8 s and t = 10 s?

3.What is the fish’s average velocity between t = 0 and t = 10 s?

4.What is the fish’s instantaneous velocity at t = 8 s?

5.Estimate the fish’s instantaneous velocity at t = 5 s.