Who first discovered what causes illness?

When does the circulatory system work with the respiratory system? a. during blood cell formation b. during cellular respiration c. during intestinal digestion d. during a viral infection

What type of organism is a one-celled organism that functions as a single unit? a. bi-celled b. single-celled c. pre-celled d. multi-celled

Areal dna molecule consists of thousands of these pairs of nucleotides. what is the pairing arrangement of the nitrogen bases