Depending upon their shape, bacteria can be classified as
(a) Coccus, Bacillus, Spiral
(b) Coccus, Helix, Spiral
(c) Coccus, Spiral, Spindle
(d) Spiral, Helix, Bacillus

Hint: It single-celled microorganisms with prokaryotic cells, which are single cells that do not have organelles or a true nucleus and are less complex than eukaryotic cells. The cell wall also makes Gram staining possible.

Complete answer:
Bacteria are found in three basic shapes as spherical shape i.e., Coccus; rod-shaped i.e., bacillus and curved shaped i.e., spirilla
Staphylococcus is an example of coccus shaped bacteria.
Streptobacillus is an example of rod-shaped bacteria.
Vibrio is an example of curved shaped bacteria.

Additional Information:
The bacteria originally first emerged on Earth around 4 billion years back, and they were the first forms of life on Earth. Bacteria and archaea were the most prevalent kinds of organisms on Earth for 3 billion years ago. Multicellular eukaryotes didn’t show up until around 1.6-2 billion years ago.

The bacteria are single-celled organisms. And they lack organelles, for example, chloroplasts and mitochondria, and they don’t have the true nucleus found in eukaryotic cells. Rather, their DNA, a double-strand that is continuous and circular, is situated in a nucleoid. The nucleoid is an irregularly shaped area that doesn’t have a nuclear membrane. Bacteria also have a cell membrane and a cell wall that is frequently formed by peptidoglycan.
So the correct answer is ‘Coccus, Bacillus, Spiral’.

Note: Reproduction happens with the help of binary fission, which is the splitting of a bacterial cell after it arrives at a specific size. Bacteria reproduce asexually, so the two daughter cells that result from binary fission have similar DNA as the parent cell. Nonetheless, a few bacteria can also exchange genetic material among each other in a cycle called horizontal gene transfer.