It has to do with the noun before "of sentence". When you use "type", "kind", breed", etc., it is logical to speak of types of pencil (one object, two or more types) or breeds of dog (one species, many types), or kinds of salad (one food group, several types). That said, many people pluralize the noun after "of" despite the logic. That gives us 3 and 4. 1 is the best, but it can't be used if there are more than one type, kind, breed, etc. 2 is clearly wrong.Originally Posted by jeab
In your example, all the sentences were of one type, so "this type of sentence" is the best choice.