Which answer choice does not contain any punctuation errors?
a.
she mentioned that, grapes can be grown on flat land, hills, along rivers, or atop mountains.
b.
eugene mentioned, "in russia, one day a year is called national flag day".
c.
"near my house," said ms. martin, "someone parked a bright-red sports car."
d.
he commented "thousands of tricolor flags are flown on that day."