フリー問題

問題文

An email writes a row into a tracking table for every recipient. Sends that use the insert function fail with a duplicate key error. What explains this?

選択肢

1. The script for a send runs on the client after delivery, so a row that the reading application created is present when the insert runs.
2. The script for a send runs once per recipient before the send, so a row that the previous recipient created is present when the insert runs.
3. The script for a send runs as one batch at the end of the send, so a row that the send itself already created is present when the insert runs.
4. The script for a send runs inside the query activity, so a row that the scheduled query created is present when the insert runs.