问题如下：
The last payment in a partially amortizing residential mortgage loan is best referred to as a:
选项：
A.waterfall.
B.principal repayment
C.balloon payment.
解释：
C is correct.
In a partially amortizing loan, the sum of all the scheduled principal repayments is less than the amount borrowed. The last payment is for the remaining unpaid mortgage balance and is called the "balloon payment."
请问B什么意思？
