To fight a bacterial infection, a patient was given an antibiotic to take for 10 days. After the patient finished taking the antibiotics as directed, almost all the bacteria were killed. After another 10 days, the patient was sick again with the same type of infection.
A | Few bacteria survived the antibiotics and stopped reproducing.
B | The patient's high fever inactivated the antibiotic, allowing the surviving bacteria to grow rapidly.
C | The antibiotic slowed the life cycle of the bacteria.
D | Some of the bacteria were resistant to the antibiotic, and they reproduced.
The beginning of autumn in North America is in September, but the beginning of autumn in South America is in March. The diagram shows the positions of Earth, the moon, and the sun on one day in September and one day in March.
F | Earth's orbit around the sun is not a perfect circle.
G | North America has a larger landmass than South America.
H | The moon has a greater pull on South America than on North America.
J | Earth's axis has a 23.5° tilt.
Some areas of an ocean are known as dead zones. These zones form when excess organic material decomposes. This increased decomposition uses up the oxygen from the water.
A | Offshore oil drilling, because water in dead zones is toxic.
B | Commercial fishing, because fish cannot survive without oxygen.
C | Commercial shipping, because dead zones change the course of ocean currents.
D | Sand mining, because oxygen is not available to form the sands on ocean beaches.