Which of the following sentences correctly uses plural forms of verbs?

A. Every Friday, the nanny watchs the children at the water park but worries that something will happen to them.
B. Every Friday, the nanny watches the children at the water park but worries that something will happen to them.
C. Every Friday, the nanny watchs the children at the water park but worrys that something will happen to them.
D. Every Friday, the nanny watches the children at the water park but worrys that something will happen to them.