B (12 inches = 1 foot) and D (1 gross = 144)
Work Step by Step
a) Pi is not exact, since it is not a whole number, and its exact value is unknown. b) The number is whole, and its value is exactly known by definition, so it has an unlimited number of significant figures. c) Although the number is whole, it represents the result of a measurement, so it has 2 significant figures and is not unlimited. d) Same as b) above.