为何用is而不用are?

有一读者问: 有这样一句话:

(1)A few attempts to board or exit a crowded bus, or to try and buy stamps in a crowded post office, may suggest to some Americans that the legendary Chinese patience and politeness is a myth.

这里为什么用is a myth而不用are a myth?

这是因为其主语the legendary Chinese patience and politeness(忍耐与谦让)已被视作一种美德、一种概念了。再如:

(2)Rest and quiet is what you want.

(3)Violence and death in the street was something that the detective viewed as a natural part of life.

(4)Soapy reached one of the avenues to the east where the glitter and turmoil was but faint.

(5)The gracious hospitality and friendliness of the Chinese was greatly appreciated by the 60 visitors on the tour.

以上所谈的表示一种概念的主语都是与上述句(1)中the legendary Chinese patience and politeness相类似,由两个抽象名词构成的。关