a series...is/are

在英语里，主语与谓语动词的一致关系存在着三个原则：语法一致原则，概念一致原则和接近原则。有时候这三个原则是会发生矛盾的。如果遵循语法一致原则，就会违背概念一致原则，或者相反。例如，five years(weeks, months) is... ten dollars is, the audience are, a number of... are, a lot of... are 便是遵循概念一致原则而违背语法一致原则的例子。而 many a man is, a series of Ns is，则是遵循语法一致原则而违背概念一致原则的例子。我们英语学习者只能逐个记忆，而不能单纯依靠推理。但是要记住，规定语法学家以及各类标准英语考试的测试专家往往趋向于语法一致的原则。

下面的英语试题要求遵守语法一致原则：

1. At last, late in the afternoon, a long line of flags and colored umbrellas were seen moving toward the gate of the palace. (TOEFL)

2. A series of lectures are to be given to mark the centennial anniversary of the founding of the school.

3. That set of four records, $\frac{\text{offered}}{\text{A}}$ for a limited time $\frac{\text{only}}{\text{B}}$ , $\frac{\text{are}}{\text{C}}$ available $\frac{\text{exclusively}}{\text{D}}$ in the storesmentioned. (TOEFL)

4. The kind of books $\frac{\text{an}}{\text{A}}$ author writes $\frac{\text{B}}{\text{C}}$ depend on the kind of man he is.

5. A large collection of contemporary photographs, including some taken by Henry, are on display at the museum. (TOEFL)

6. This group, among whom are Jean and Eddie, certainly were the life of the party. (TOEFL)

[附注] a series of + 复数名词作主语时, 其谓语动词要用单数, 这是英语测试的要求。但是, 在英语原著中有时也会看到 a series of + 复数名词使用动词复数的实例:

A series of profit downgradings were shrugged off. (Longman Grammar of Spoken and Written English, p.185)。一系列的利润下降没有被重视。