In a shop ___ custom

In a shop ___ customers.A.it is important pleasedB.it is important to pleaseC.there is important to pleaseD.there is important pleasing

参考答案：
B解析there is表示有，这是it作形式主语，不定式做真正主语的句子。句意是：在一家商店，取悦于客人是很重要的