Choose the letter A, B, C or D the word that has the underlined part different from others

I. Choose the letter A, B, C or D the word that has the underlined part different from others. 1. A. aquatic B. cause C. effect D. race 2. A. earplug B. hear C. pear D. clear 3. A. radioactive B. pollution C. contaminate D. convey 4. A. official B. cattle C. icon D. Scottish