1．(2018·全国卷Ⅰ)While running regularly can't make you live forever, the review says it ________ (be) more effective at lengthening life than walking, cycling or swimming.
解析：is 根据语境可知，此处叙述的是一般的客观事实，且本句中宾语从句与主句的时态应保持一致，故使用一般现在时。it指代上一句的running regularly，是第三人称单数，故填is。
2．(2017·全国卷Ⅰ)Fast food ________ (be) full of fat and salt; by eating more fast food people will get more salt and fat than they need in their diet.
解析：is 本句中的主语是fast food，是不可数名词短语，所以谓语用第三人称单数形式，且此处讲的是现状，所以填is。
3．(2016·全国卷Ⅱ)Leaving the less important things until tomorrow ________ (be) often acceptable.
解析：is 主语是“Leaving the less important things until tomorrow”，所以谓语用单数形式；此处表示客观情况，用一般现在时。
