Which of the following letter-number clusters will replace the question mark (?) in the given series to make it logically complete?
JNR -1, LPO -2, NRL -4, ?, RVF -16
AIJT-6
BPTI-8
CQRT-9
DTOR-7
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AIJT-6
BPTI-8
CQRT-9
DTOR-7