A. Diplococcus: Refers to spherical bacteria arranged in pairs (two cells). This does not describe chains. B. Staphylococcus, streptococcus: Staphylococcus describes clusters of cocci and Streptococcus describes chains -this choice reverses the order asked (chains - clusters). C. Streptococcus, staphylococcus: Strepto- are chains of spherical cells and Staphylo- are clusters of spherical cells. D. Micrococcus, diplococcus: Micrococcus is a genus of cocci (often in tetrads or irregular clusters) and diplococcus means pairs.