A copy machine makes 60 copies per minute. A second copy machine makes 80 copies per minute. The second machine starts making copies 2 minutes after the first machine starts. Both machines stop making copies 8 minutes after the first machine started. Together, the 2 machines made how many copies?

单项选择题According to the Protein Hypothesis, which of the following observations provides the strongest evidence that genes are NOT composed of DNA ?

单项选择题According to the passage, a similarity between DNA and proteins is that both types of molecules:

单项选择题A student claimed that polycarbonate is more dense than PA-6. Do the results of Experiments 1-3 support his claim?

单项选择题One marble is to be drawn randomly from a bag that contains three red marbles, two blue marbles, and one green marble. What is the probability of drawing a blue marble?

单项选择题A student claimed that “If the masses of 1 cm3of any solid and 1 cm3of any liquid are compared, the massof the solid will be greater.” Do the data in Table 1support his claim?

单项选择题Consider the following hypothesis: In a circuit arranged as in Figure 1 containing a battery, a capaci-tor, and a constant resistance, as capacitance increases,the time required to reach a given voltage across thecapacitor increases. Do the experiments support thishypothesis?

单项选择题The tall dark girl’s marriage to Doctor Reef proves to be a _____ one

单项选择题The clouds have_______ the sun.

单项选择题A flight instructor charges $50 per lesson, plus an additional fee for the use of his plane. The charge forthe use of the plane varies directly with the square root of the time the plane is used. If a lesson plus 16 minutes of plane usage costs $90, what is the total amount charged for a lesson having 36 minutes of plane usage?

单项选择题When graphed in the standard (x,y) coordinate plane, the lines x= –3 and y=x–3 intersect at what point?