Which of these things is not related to the others?

C.

Ok, this one was difficult.  An ampule is a small, sealed vial used to preserve a sample. A, B, and D are different types of stems on a vine.  A petiole is the stem that connects a leaf to a vine.  The stem that connects a grape cluster to a vine is known as a peduncle.  And a tendril is the slender forked stem that coils around trellis wires, securing the vine’s long, leafy arms in an upright position.