Which two body systems work together to deliver oxygen through the body? A. digestive and excretory
B. reproductive and endocrine
C. circulatory and respiratory
D. nervous and digestive

please no gibberish or random letters i need help

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