I was reading about Subject-Verb agreement from a grammar book I have, and I came about some of these examples:
1.The behavior of the children were excellent. [Here were must be was in order to agree with behavior.]
2.Not one of his lectures have ever been printed.[The subject is one, not lectures; therefore, have should be has.]
3.By that time two weeks' salary were due.[Here again, the subject is salary, not weeks; therefore, were should be was.]
4.The quality of the mangoes was (not were) good.
5.The cost of all these articles has (not have) risen.
6.A series of lectures has (not have) been arranged on the subject
7.A variety of pleasing objects charms (not charm) the eye.
I understood the first three examples as there was explanation for them. In the fourth example, the subject is quality so we used singular verb. In the fifth example, cost is the subject and hence, we used singular verb again.
What I didn't get is the sixth and seventh example. Is the subject in sixth example is series? what is the subject in the seventh example?