In the following questions, there is a relationship between the letters / numbers / figures on the left of the sign (: :). The same relationship exists to the right of the sign (: :), of which one is missing. Find the missing term from the given alternatives.
C E H L : P L I G : : L N Q U : ?
1. P Y U R
2. Y U P R
3. Y U R P
4. Y P U R