You may spell it "field" or "fields" whether dropping one or many fields.
If you are dropping multiple fields, there is a significant performance difference between using one DROP statement vs multiple DROP statements that drop one field each.
DROP FIELD a,b,c;
is faster than
DROP FIELD a;
DROP FIELD b;
DROP FIELD c;
The reason is that QV rewrites the records array after every DROP statement, which can take a few seconds in a large table. This may be less of an issue in QV12, haven't benchmarked it.