Complete the following sentence

Complete the following sentence with a (compound) word derived from the one(s) given in bracket.

Instinct is the （ ） tendency that a person or animal has to behave or react in a particular way. (nature)

根据后文tendency名词和前文the，说明这里应该填修饰名词的形容词，nature的形容词为natural。句意：本能是人或动物必须以一种特定方式表现或反应的自然倾向。