jq Quiz: map, select, empty and Missing Values

jq Quiz: map, select, empty and Missing Values

Choose one answer. Each attempt draws 10 of 20 questions; the practice pass mark is 8/10. Original topic practice, not an official exam. Predict jq 1.6 filters over JSON arrays, optional access and fallback values.
1 of 10
With jq -nc, what JSON is emitted?
jq
[{"n":2},{"n":7}] | map(.n) | add