The 2.75'' deep switch box is the smallest among the options that can contain a three-way switch, an external type MC connector, and one 12AWG ground wire with a single cable entering the box. Option A is correct.
To determine the smallest box that can accommodate one three-way switch, an external type MC connector, and one 12AWG ground with only one cable entering the box, you need to consider the space required for the switch, connector, and the wiring.
Let's evaluate each option:
a. 2.75'' deep switch box: This option provides enough depth to accommodate the switch, connector, and wiring. It should be sufficient.
b. 2 1/8" deep device box: This may be too shallow to comfortably fit all the components, and it might not provide enough space for proper wire bending.
c. 1 1/4" deep 4"-SQ with 2.2 in^3 p-ring: This option is likely too shallow to accommodate the switch, connector, and wiring adequately.
d. 3 1/2" deep masonry box: This option provides sufficient depth, but it might be larger than necessary. However, it would certainly work.
Considering the options, the most suitable box among those listed is likely:
a. 2.75'' deep switch box
It provides enough depth to comfortably accommodate the switch, external type MC connector, and the 12AWG ground wire.
The complete question is:
Among those shown below, which is the smallest permitted to contain one three-way switch, an externals type MC connector, and one 12AWG ground? Only one cable enters the box and all conductors connect to the switch.
a. 2.75'' deep switch box
b. 2 1/8" deep device box
c. 1 1/4 " deep 4 "-SQ with 2.2 in^3 p-ring
d. 3 1/2 " deep masonry box