The below statement corresponds to a numbered sentence in the passage. It contains a blank and is followed by four answer choices. Decide which choice fits best in the blank. The word or phrase that you choose must express roughly the same meaning as the italicized word in the passage. Write the letter of your choice on the answer line.

The branches of the Nile move in a $\underline{?}$ course through the Sahara Desert and over the Aswan Dam. ___________ (serpentine)

a. direct b. snakelike c. complex d. standard