Final answer:
Toxoplasma gondii is the parasite of utmost concern due to the potential harm it can cause to the fetus/child.
Step-by-step explanation:
Of the given options, the parasite of utmost concern due to the potential harm it can cause to the fetus/child is Toxoplasma gondii. Toxoplasma gondii is a protozoan parasite that can cause serious infections in pregnant women and their developing fetuses. Cats are the definitive host of Toxoplasma gondii, and the infection can be contracted by coming into contact with the parasite in cat feces, unwashed fruits and vegetables, or undercooked meat.