Find the word which has a different sound in the underlined part in each line

find the word which has a different sound in the underlined part in each line
1.a. space  b. taxi   c. airplane   d. safety
2.a. prefer   b. expensive  c. believe   d. energy
2.a. underwater   b. umbrella  c. universe   d. understand
4.a. today   b. travel   c. handle    d. transport