The Basic Conjoint Analysis Model Expressing the Fundamental Relationship Between $$U ( X ) = \sum _ { i = 1 } ^ { m } \sum _ { j = 1 } ^ { k i } \alpha _ { i j } X _ { i j }$$

The basic conjoint analysis model expressing the fundamental relationship between attributes and utility in conjoint analysis is shown below:
$$U ( X ) = \sum _ { i = 1 } ^ { m } \sum _ { j = 1 } ^ { k i } \alpha _ { i j } X _ { i j }$$
What does ki represent?

A) number of levels of attribute i
B) number of attributes
C) the part-worth contribution or utility associated with jth level (j,j=1,2,...ki) of the ith attribute (i,i=1,2,...m)
D) 1 if the jth level of the ith attribute is present,or 0 otherwise