Final answer:
The pathogen responsible for the symptoms in the 2-year-old boy is most likely the herpes simplex virus (HSV-1), which causes herpetic gingivostomatitis. Symptoms include swollen gums, vesicular, inflamed lesions on the hard palate and lips, and enlarged and tender cervical lymph nodes.
Step-by-step explanation:
The pathogen responsible for the symptoms in the 2-year-old boy is most likely the herpes simplex virus (HSV-1). This virus commonly causes herpetic gingivostomatitis, which is characterized by swollen gums and vesicular, inflamed lesions on the hard palate and lips. The enlarged and tender cervical lymph nodes are also indicative of an infection caused by HSV-1.