Amylase is now frequently prepared with lactose or other sugars as extenders. Determine which experiments would give erroneous results if contaminated amylase were used.

That's odd. Well, contaminated amylase would give you false positives; any experiment that requires it would potentially give erroneous results then? Without much more to go off of, I guess you could definitely say 2 and 4, though apart from that I guess you can't really be too sure.