单项选择题 They haven’t decided ______ the microscope themselves or buy one from the United States.

单项选择题 The old man came upstairs with great efforts, his right hand ______ a stick for support.

填空题 For centuries, people have been enjoying the rich flavor of chocolate, a (1) made from a plant. Most people today think of chocolate as something sweet to eat or drink that can be easily found in (2) around the world. It might surprise you that chocolate was once highly treasured. Researches at the University of Pennsylvania recently (3) a study. It suggested that people in Central and South America first gathered the cacao plant much earlier and for a different use than (4) once thought. The researchers examined the (5) of substances found in ancient clay containers that were over three thousands years old. They discovered that the substance came from an alcoholic drink made from the (6) of the cacao plant. The researchers believe it was the interest in cacao as an alcoholic drink that led to the use of its bitter seeds to make what is now known as chocolate.