InQuizitive Editing the Errors that Matter Practice Test

The idea being tested is how to form possessives for two owners. When an owner is plural and ends with s, you make the possessive by adding only an apostrophe after that s. The first owner here is Garcias, which implies more than one Garcia; their possession is Garcias'. The second owner is Smith, a singular name, so its possessive is Smith's. Put together with “and,” this makes Garcias' and Smith's students, meaning two sets of students owned by the Garcias and by Smith. Using Garcia's would imply a single Garcia, and using Smiths would imply multiple Smiths, which doesn’t fit the intended two distinct owners.