Answer:
The correct answer would be cocci or coccus shaped bacteria (probably Streptococcus)
Explanation:
Bacteria cells are of different shapes such as Cocci or coccus (singular) which means they are round in shape.
Bacilli or bacillus (singular) are rod-shaped.
Spirilla or spirillum (singular) are curved shaped bacteria that can range from a gentle curved to a corkscrew spiral shaped.
Major bacteria present in yogurt are lactobacillus and Streptococcus spp. so observed bacteria specimen can be streptococcus spp. bacteria.
Thus, the correct answer would be cocci or coccus shaped bacteria.