The correct answer is B.

Stop: The answer choices reflect different processes that occur during meiosis.

Think: Synapsis occurs during prophase I of the first meiotic division. It is during this time that crossing over can occur. Crossing over is when chromatids of homologous chromosomes break at corresponding points and exchange equivalent pieces of DNA. The points of contact between these chromosomes where crossing over occurs are called chiasmata.

Predict: For crossing over to occur, homologous chromosomes must be aligned and touching each other. Without this they will not be able to exchange pieces of DNA.

Match: (B) is the correct answer.

(A) occurs during prophase I and is necessary for synapsis to occur because chromosomes must be appropriately formed but is not a part of synapsis.

(C) occurs during metaphase I, after crossing over has already occurred.

If (D) occurs, it is called nondisjunction and generally happens during anaphase. This occurs after synapsis takes place and results in daughter cells have an inappropriate number of chromosomes.

(E) occurs during prophase I but before synapsis takes place.