Which one of these has a Chinese letter arrangement?

The correct option is Corynebacterium diphtheriae.

Here is a step-by-step explanation of why this is correct:

1. Understanding the Cellular Arrangement:
Corynebacterium diphtheriae is a Gram-positive, rod-shaped bacterium (bacillus). When these bacteria divide, they undergo a unique process known as snapping division. During binary fission, the inner layer of the cell wall divides, but the outer layer remains attached on one side, acting as a hinge.

2. The Formation of the "Chinese Letter" Pattern:
Because of this hinge-like mechanism, the daughter cells snap at sharp angles to each other after division. This causes them to arrange themselves in characteristic formations that resemble the letters V, L, or parallel clusters (palisades). Under a microscope, this distinct angular grouping strongly resembles the strokes of Chinese calligraphy characters, which is why it is classically described as a "Chinese letter" arrangement.

3. Comparing with Other Options:
Let us look at the other bacteria listed to see why they do not match this description:
- Clostridium tetani: Typically appears as individual rods with round, terminal spores, giving them a characteristic "drumstick" or "tennis racket" appearance.
- Mycobacterium tuberculosis: Often forms straight or slightly curved rods that tend to clump together or form parallel bundles called "serpentine cords" due to cord factor in their cell wall.
- Bacillus anthracis: Characteristically forms long chains of large, square-ended rods, often described as having a "bamboo-rod" appearance.

Therefore, the classic "Chinese letter" cellular arrangement is a key microscopic diagnostic feature specifically associated with Corynebacterium diphtheriae.