It is: 70
The least common denominator (LCD) refers to a multiple that is COMMON to two or more numbers. You have only one number in the question! The least denominator for a number is itself.
The common denominator is 28.
A common denominator, though not the least, is 168.
A common denominator, though not the least one, is 14*49 = 686.
A common denominator, though not the least one, is 14*12 = 168.
The least common denominator is 70.
The LCD of 10/11 and 1/14 is 154.
There is none because the Least Common Denominator (or LCD) is the Least Common Multiple (LCM) of the denominators of a pair of fractions.
You need at least one more fraction in order to have a common denominator.