A recreational vessel 50 feet in length has an approved fixed fire extinguishing system in the machinery space. The minimum number of 5-B portable extinguishers required is ______.

Why C is correct

Table 1 to 33 CFR §175.320(a)(1) shows that a vessel 40 feet or more but not more than 65 feet requires 3 extinguishers without a fixed system, but only 1 when a fixed fire extinguishing system is installed in the machinery space.