Complete the sentences with a word derived from the one in brackets.
Current research indicates a （ ）relationship between all forms of smoking and cancer of the mouth and throat.(cause)
【正确答案】：CAUSAL
【题目解析】：
目前的研究表明，所有形式的吸烟与口腔和喉咙癌症之间存在因果关系。causal具有因果关系的，形容词。