What is the rule with stem changers in the preterite tense

Kiko is writing an introduction for an article about the red panda. read what she has so far. what has red fur and a ringed tail, and is as big as a housecat? why, a panda, of course! the red panda doesn’t look much like its black-and-white cousin, the giant panda, but the two actually have a lot in common. which of the following should she add to her introduction? a. a clear central idea b. an opening that grabs the reader’s attention c. a statement previewing what points the essay will compare d. a statement that summarizes kiko’s opinions about the animals