Грамматика и Лексика

Преобразуйте, если это необходимо, слово HAVE так, чтобы оно грамматически соответствовало содержанию текста.

Besides, you can use the Internet, which is the greatest resource of knowledge that mankind ___________ (ever). But remember! You will not get any better without speaking and listening to the language. No matter what path you take in learning a new language, this is by far the most important step.