You are south and you pick up:

♠ J 10 5 4 2
♥ Q 10 5 4 3
♦ 5
♣ Q 2

¹ strong

What is your bid?

A 2 ♠
B 2 ♥
C 2 ♦

A 2 ♠ (20 votes)
Not the right answer.

B 2 ♥ (8 votes)
Not the right answer.

C 2 ♦ (55 votes)
The correct bid is 2♦.
North can hold two types of hand:
- a game forcing hand with a long suit
- a balanced hand of 23 points or more.
In both cases he is not helped by south bidding a weak suit. That would only consume precious bidding space, which north needs to describe his hand.
Therefore the partner of the strong hand should normally bid 2♦, a waiting bid allowing the strong hand to indicate his type of hand.
Often the 2♣-opener will now rebid 2NT whereafter the bidding continues like after a 2NT-opening. This way the strong hand usually will become declarer. 

Do not exaggerate though: the weak hand is not obliged to bid 2♦. He can bid 2♥ or 2♠. These bids show at least a five card suit with at least two out of the three top honour cards. That usually is valuable information for the strong hand.