The student groups constructed and tested the electromagnets. What was key to maximizing the electromagnet's strength? A. The absence or presence of a switch.
B. The length of wire and number of coils.
C. Whether or not the students used an iron core.
D. The size of the battery and amount of electrical energy.

Which of these statements is true about autotrophs, but not heterotrophs? a. they use sugar and oxygen to make carbon dioxide and water.b. they use chlorophyll and oxygen to make carbon dioxide and water.c. they use sunlight, water, and carbon dioxide to make sugars.d. they use sunlight, water, and oxygen to make chlorophyll.