Which of the following is true in order to successfully implement PSD2? ( ).

参考解析：

根据题干关键词“to successfully implement PSD2”，定位到最后一段"The gap between writing rules and implementing them is always large. ..."从First, consent from customers to provide access to their bank data must be gained explicitly, and the purposes of the data use should be clearly explained. 可以看出，要实施PSD2，必须征得客户的明确同意，并且说明使用数据的目的。A项的“are forced to”用词不当，语气上，该规定并未强迫客户…，而是要去征求客户的同意，故排除；B项错在“their entire operational system”原文未提及，且语义过于绝对。排除；从Second, regulators must be very tough both in ensuring .... Third, regulators must also be flexible enough to ...可看出，监管者既要严格，又要有一定的灵活度，故C项正确。从Since the new entrants will not be licensed to engage in riskier financial activities—such as lending money—it makes sense to regulate them with a lighter touch. But if some Fintech providers do end up becoming systemically important, higher standards of oversight might be necessary可知，以及结合原文第二段The rules will compel banks to share data easily with licensed third parties可知，该句中的“new entrants”是指“third parties”，而D项错在“Banks and third parties”。且原文是“with a lighter touch”，而D项是“with a light touch”，也有细微的区别。故排除D。故本题正确答案选C。