दी गई श्रृंखला में निम्नलिखित में से कौन सा अक्षर समूह रिक्त स्थान () को प्रतिस्थापित करेगा? BMM, DOO, ______, HSS, JUU

Which number will replace the question mark (?) in the following series? 83, 79, 71, 67, 59, 55, ?

Which of the following letter-number clusters will replace the question mark (?) in the given series to make it logically complete? HLE23, JJH21, LHK19, NFN17, ?