Red blood cells are generally 8 m in diameter. Given the choices of virus, bacteria, protozoa, or helminths, what might the rings and crosses (see arrows) be? And why? Bacteria. Due to size and shape. Virus. Due to size and shape. Helminths. Due to size and shape. Protozoa. Due to size and shape. Bacteria. Due to color. Helminths. Due to color. Virus. Due to color. Protozoa. Due to color.