Which of the following organisms possesses a true nucleus?

Step-by-step solution

Organisms possessing a true nucleus are eukaryotes. Penicillium is a fungus and belongs to the eukaryotes, hence it possesses a true, membrane-bound nucleus. Nostoc (a cyanobacterium), Methanococcus (an archaebacterium), and Lactobacillus (a eubacterium) are all prokaryotes belonging to the kingdom Monera. They lack a true nucleus and membrane-bound organelles. Answer: Penicillium