उत्पत्ति (प्राकृतिक या कृत्रिम) के आधार पर निम्नलिखित में से कौन-सा विषम (भिन्न) है?

Four letter-pairs are given below. The letters on the left side of (-) are related to the letters on the right side following a specific logic/rule. Three of them share the same rule. Select the odd one out.

Four letter-pairs are given. The letters on the left side of (-) are related to the letters on the right side of (-) by some logic. Three of them follow the same logic. Select the odd one out.