У меня три простых вопроса по синтаксису JavaScript [требует правки]

№1 A property that does not exist has which of the following values?

Question 5 options:

A)
null

B)
Infinity

C)
NaN

D)
undefined

№2 If we have a book object but we do not give it a "subtitle" property, the following code will return undefined.

bar len = book.subtitle.length;

Question 6 options: True False

№3 The following code correctly deletes a property.

delete book.isbn;

Question 7 options: True False