Preimplantation diagnosis

Correct Answer: A

Rationale: The correct answer is A because preimplantation diagnosis involves screening embryos for genetic abnormalities before they are transferred to the uterus, allowing for the exclusion of abnormal embryos. This ensures that only healthy embryos are selected for implantation, increasing the chances of a successful pregnancy. Choice B is incorrect because preimplantation diagnosis is not done for the creation of stem cells but rather to identify genetic abnormalities. Choice C is incorrect because the purpose of preimplantation diagnosis is not to make decisions about terminating pregnancies but to select healthy embryos for transfer. Choice D is incorrect because preimplantation diagnosis must be done before implantation to identify abnormal embryos and avoid transferring them.

Correct Answer: D

Rationale: Certainly! The correct answer is D because both ionizing and non-ionizing radiation originate from the sun (A), are part of the electromagnetic spectrum (C), and have the potential to cause cancer (B) depending on the dose and exposure. Ionizing radiation has higher energy and can directly damage DNA, leading to cancer. Non-ionizing radiation has lower energy but can still cause harm, such as skin burns or increasing cancer risk with prolonged exposure. Therefore, all of the above choices are correct as they accurately describe characteristics of both types of radiation.

Correct Answer: B

Rationale: The correct answer is B (50%). This is because empirical data shows that around half of Americans live in areas with poor air quality due to factors like pollution, industrial activities, and traffic congestion. Choice A (10%) is too low and underestimates the prevalence of poor air quality in the US. Choice C (75%) is too high and exaggerates the problem, as not three-quarters of Americans are affected. Choice D (90%) is also an overestimation, as the majority but not almost all Americans are impacted by poor air quality. Therefore, B is the most accurate representation of the proportion of Americans living in areas with poor air quality.

Correct Answer: C

Rationale: The correct answer is C: Evaporation and precipitation. These two processes are fundamental to the hydrological cycle. Evaporation is the process where water is converted from liquid to vapor and enters the atmosphere, while precipitation is when water vapor condenses and falls back to the Earth as rain, snow, sleet, or hail. This cycle is essential for maintaining Earth's water balance. A: Coagulation and sedimentation are processes used in water treatment to remove impurities, but they are not part of the hydrological cycle. B: Filtration and disinfection are also water treatment processes and do not directly involve the movement of water through the hydrological cycle. D: Chlorination and fluorination are methods used for water disinfection but do not play a role in the natural hydrological cycle.

Correct Answer: B

Rationale: The correct answer is B because air pollutants like sulfur dioxide and nitrogen oxides can mix with moisture in the air to form acidic compounds. When these acidic compounds dissolve in rainwater or dew, they can damage forests and buildings by causing corrosion, deterioration of materials, and harming plant life. Particulates (choices A and C) can physically damage surfaces but do not directly cause the chemical reactions that lead to harm. Dehydration of surfaces (choice D) is not a significant mechanism for the harm caused by air pollution to forests and buildings.