Crossing over during meiosis occurs at four strand stage. This is proved by the observation that:

• A. rarely all four gametes resulting from a meiotic division could be recombinants.
• B. usually only two gametes resulting from meiotic division could be recombinants.
• C. chaismata are seen only at the four strand stage.
• D. occasionally none of the four gametes resulting from meiosis could be a recombinant.