What two of the three challenges listed prevented Europeans from penetrating Africa until the late 19th century?

Which organisims can cause diseases a. micro organisims b. multicellular organisnims c. both d. neither

What drifted apart millions of years ago to create two different worlds

Which of the following ideas would not lead to lower amounts of waste? a) the extension of a product’s lifetime b) the elimination of unnecessary packaging c) flexible construction for simple repair d) built-in obsolescence e) the introduction of new design technology