An engineer tests three new ceramic parts, each of which could potentially replace a steel part inside an automotive engine. The three parts, identical in size, are each made of a different ceramic compound. The parts are heated to the same temperature and placed under the same stress loads. At the end of the test, the engineer concludes Part B is the best for the job. What was the independent variable in this test? Select one:

a. dimensions of the parts

b. temperatures to which the parts were heated

c. the engine used to test the parts

d. the composition of the parts

Populations of blue-winged warblers, a type of bird, migrate south in the winter and return to canadian breeding grounds in the spring. as global temperatures have increased due to climate change, spring has started arriving in the warbler's breeding grounds earlier in the year, before the warblers return. warblers now arrive at their breeding grounds too late to select ideal nesting sites and to feed on important early-spring food sources how are populations of blue-winged warblers most likely to be affected by the earlier arrival of spring? o a. populations will go extinct since the warblers will stop migrating to breeding grounds. b. populations will be unaffected since most species can quickly adapt to effects of climate change. c. populations will increase since warmer temperatures are generally beneficial to survival, d. populations will decline since individuals will be less likely to successfully reproduce, reset next

Which sentence best describes the relationship between chlorophyll and the chloroplast? a.)chlorophyll is a chemical found in a chloroplast. b.) chloroplast is a chemical found in a chlorophyll. c.) both chlorophyll and chloroplasts are found in animals. d.) both chlorophyll and chloroplasts make carbon dioxide.

What sentence best supports the statement that hormones are involved in the regulation of homeostasis? a. the hormone erythropoeitin increases the production of red blood cells when oxygen levels are low. b. the hormone oxytocin promotes labor contractions of the uterus during childbirth. c. the hormone melatonin induces sleep and its production is slowed by exposure to light. d. the hormone cortisol suppresses the immune system and is produced when the body is under stress.