When riding in a group, under what circumstances should the staggered formation be avoided?

Answer: C — Making turns

When riding in a group, the staggered formation should be avoided when making turns. This is because when making turns, the formation can become unsafe and riders may unintentionally collide with each other. It is important to maintain a single-file formation when making turns in order to ensure the safety of everyone in the group. Options A, B, and D are incorrect because riding in a staggered formation is generally safe and efficient on city roads, highways with light traffic, and at stoplights.