How should the developer write this AMP script conditional statement?

A developer wants to include an AMP script if/else statement in an email to satisfy the condition "if the subscriber’s tier is not premier then display heading encouraging them to upgrade." The tier value has already been set as variable named @level.

How should the developer write this AMP script conditional statement?
A . %%[IF @level == ‘premier’ THEN SET @message = You are premier member
B . " ENDIF IF @level == ‘premier’ THEN SET @message = ‘Upgrade to premier now
C . ‘" ENDIF]%% %%=v(message)=%%%%=IF(@level IS ‘premier’, Upgrade to premier now! You are a premier member%%=IIF(@level = ‘premier’, ‘You are a premier member!’, Upgrade to premier now!
D . %%=IIF @level == premier, You are a premier member" Upgrade to premier now!
E . %%IF(@level == ‘premier’) THEN ‘Upgrade to premier now!’ ELSE ‘You are a premier member’ ENDIF]%%

Answer: C