An opening bid at the two-level shows
(A) Defined 6-10 HCP
(B) Five+ card major AND a four+ card minor
Response
(a) 2NT asking for the minor (searching for possible game, or
(b) 3C to play in the minor (opener correct to 3D if necessary)
Variant (Johan Longueville) Over 2NT opener responds
3C=4 card in clubs
3D =4 cards in diamonds
4H = 5 cards in clubs
4S = 5 cards in diamonds