Which revision corrects Sam’s error in the use of dashes to set off a clause in sentence 4? a The longhorns had been skittish, but Johnny Chillers, who was named for the old Chillers trail, sang to them—whenever they started to spook—to calm them down. b The longhorns had been skittish, but Johnny Chillers—who was named for the old Chillers trail sang to them—whenever they started to spook to calm them down. c The longhorns had been skittish, but Johnny Chillers—who was named for the old Chillers trail—sang to them whenever they started to spook to calm them down. d The longhorns had been skittish—but Johnny Chillers—who was named for the old Chillers trail, sang to them whenever they started to spook to calm them down.

c The longhorns had been skittish, but Johnny Chillers—who was named for the old Chillers trail—sang to them whenever they started to spook to calm them down.

Explanation:

The best revision that corrects Sam's error in the use of dashes to set off a clause is option C because it correctly separates the group of words which indicates a pause to emphasize that what Johnny Chillers was named after.

An em dash is used to show a pause and are also used to separate groups of words and their usage can be interchanged with commas or hyphens.