Which chromosome sequence could indicate a deletion event?

A deletion event refers to the loss of a segment of a chromosome, which can be indicated by a change in the sequence where certain elements are missing. In the correct choice, the sequence shows a break in continuity—specifically, the absence of the segment "def" that is present in the other options. This missing segment signifies that part of the chromosome has been deleted, thereby leading to a different sequence than what would be expected based on the complete series.

In contrast, the other sequences either represent full, uninterrupted segments of a chromosome or indicate other genetic variations that do not include a deletion. Thus, the identification of the missing portion in the correct sequence becomes a direct indicator of a deletion event on the chromosome.