Final answer:
Among the terms provided, 'tetrad' is the only one that exclusively refers to a bacterial arrangement of cells—a group of four—and not to a bacterial genus. The term 'vibrio' refers to comma-shaped prokaryotic cells. Other terms like 'streptococcus,' 'bacillus,' 'staphylococcus,' and 'sarcina' describe both the shapes and arrangements of cells and are the names of bacterial genera, with the exception of sarcina, which does not refer to a genus name. E) sarcina
Step-by-step explanation:
The terms you are asking about refer to both the shape of bacteria and, in some cases, also the name of a bacterial genus. A tetrad refers simply to a group of four bacteria typically associated with the division of cells. The term streptococcus is both a genus name and refers to a chain-like arrangement of spherical bacterial cells. Bacillus likewise is the name for rod-shaped bacteria as well as a genus. Staphylococcus is the term for a cluster-like arrangement that appears similar to a bunch of grapes, and the name of a genus. A sarcina refers to a cubical packet of eight spherical bacterial cells and does not refer to a bacterial genus name.
Answering your multiple-choice question, the prokaryotic cell that is comma-shaped is referred to as C. vibrio. Common bacterial shapes include spherical (coccus), rod-shaped (bacillus), or curved (spirillum, spirochete, or vibrio). When identifying the arrangement of bacteria, you may see terms like pairs (diplobacilli), chains (streptobacilli), clusters (staphylococcus), or tetrads. Among these terms, tetrad is the only one that refers solely to an arrangement of bacterial cells and not also to a genus name.