For real numbers a and b, when is the equation ∣a+b∣=∣a–b∣true?

单项选择题According to Study 1, white S has a reflectance of 0.98at a wavelength of 0.60 μm. This means that white Sreflects:

单项选择题Based on the results of Study 1, if the distance from the center of a 100 m ×100 m plot were 75 m from thenearest clearing, the expected average change inAGTB at the plot over 17 yr would be closest to whichof the following values?

单项选择题If, in Experiment 2, a 1.5 ×10–6F capacitor had been used, the time required for the voltage across thecapacitor to reach 6 V would have been closest to:

单项选择题According to Scientist 2’s viewpoint, compared to thealtitude at which a stony asteroid would have explodedin Earth’s atmosphere, a comet of similar size wouldmost likely have exploded at:

单项选择题Hornfelsis a metamorphic rock formed when magma(molten rock) heats sedimentary rocks on Earth’s sur-face. According to Figure 1, hornfels is most likely amember of which of the following facies?

单项选择题Which of the following factors affecting the reaction of Mg and H2O was studied in Experiment1, but not inExperiments2 or 3?

单项选择题The scientist who describes the DNA Hypothesis implies that the Protein Hypothesis is weakened by which of the following observations?

单项选择题A The need for good managers is not going away. It is intensifying. With flatter&quo

单项选择题Joelle earns her regular pay of $7.50 per hour for up to 40 hours of work in a week. For each hour over 40 hours of work in a week, Joelle is paid 1 times her regular pay. How much does Joelle earn for a week in which she works 42 hours?

单项选择题If 9(x - 9) = -11, then x = ?