Which two systems work together to ensure that all cells in the body receive oxygen

An example of internal feedback working to maintain homeostasis is your a. decreased respiration rate when you are studying b. decreased heart rate when you are sad c. increased respiration rate when your muscles need more oxygen d. increased heart rate when your lungs need more oxygen

Which of these is not a nucleotide base found in dna?

Look at the photo of the leaf, which term best describes this leaf ? a-simple.b-parallel.c-lobed.d-tooth.