SLE is associated with deficiency of early complement proteins(eg. C1q, C4, C2). (FA 19, pg. 462)
Complement is important for removing immune complexes, so patients with complement deficiencies *(c1-c4) are more likely to develop SLE. C1q is a better answer than than MBL (D) b/c the MBL pathway is triggered by bacteria.
C1q, C1r, and C1s form the C1 complex. Any time you see C1 with any of these three letters "qrs" think of C1 which is the first component of the classical complement pathway