Silicates are a group of minerals that contain what two elements?
A. silver and gold
B. silicon and oxygen
C. carbon and sodium
D. hydrogen and helium

Where do the respiratory and circulatory systems meet? a. in the heart b. in the muscles c. in the lungs d. in the brain

Any sound above what db can cause hearing loss in human beings

What's wrong with this ecological pyramid? (multiple choice)1. secondary consumers should be at the bottom of the pyramid2. the sun has an arrow leading to decomposers 3. primary consumers should come after the sun4. energy retained should increase from the bottom to the top5. the sun should be at the bottom of the pyramid