How many acres is the site for a standard house plan if it is stated to be 1/3 acre?

The designated site for a standard house plan being stated as 1/3 acre indicates that the area of the property is specifically one-third of an acre. Therefore, option B, which is 1/3 acre, accurately reflects the measurement given in the question.

To better understand this, it's important to be aware of the measurements typically used in real estate and land planning. An acre is a unit of area used in the United States and other countries that equals 43,560 square feet. When dealing with subdivisions or housing plans, precise measurements are crucial for planning and zoning. In this case, since the question specifies the site as 1/3 acre, that is the directly correct interpretation without need for conversion or comparison with other acre measurements.

The other options present different acre sizes that do not match the specified measurement, making them irrelevant to the context of the question.