------delicious the sandwich with ham and tomatoes is!a.what

------delicious the sandwich with ham and tomatoes is!a.what a b.what c.how
前面的sandwich 和ham 都为不可数 .而谓语是is .但按照what 的感叹句是否缺了一个主语呢?还是sandwich with ham 是名词而tomatoes 主语?选哪个