Read the excerpt from Into the Unknown by Stewart Ross.

It was soon clear that the Ma Robert had serious design faults. Her engine was not powerful enough to drive her upstream against strong currents, and her boiler consumed vast quantities of wood: a day’s steaming needed one and a half day’s wood-cutting. Her hull was made of thin sheets of a new kind of steel that had not been tested. It soon developed so many holes that it leaked like a colander and had to be continually pumped out. “For us, steam was no labor-saving power,” Livingstone grumbled in his journal. He called the Ma Robert all sorts of names: “the wretched little steamer,” the “tin kettle,” and “the slow puffing Asthmatic.”

Which text feature would best support the details in the excerpt?

a photograph of Charles Livingstone
an illustration of Ma Robert
a map of the African continent
a chart of the many uses of steam