Most parents make little use of baby clothing. For example, more than half of all parents dress their infants a particular garment only a few times during about a one month period before stowing that garment away. In addition, 24 percent of all parents let their babies wear any particular piece of clothing only a single time.
Question type - Weaken the argument
Conclusion - Most parents make little use of baby clothing.
Missing information - Author assumes that the cloths that the parents are buying for their infants is only being used once. Means once is used cannot be reused again by infants' siblings.
If we weaken the assumption made by the author this argument will be weakened.
D. Infants need more new clothing than adults because they grow out their existing garments quickly.
D again presumes that the cloths that the parents are buying for their infants is only being used once. This is an assumption and hence cannot be our answer. We need something to weaken this argument.
C. It is customary for most infants to wear clothes which were handed down from siblings and relatives.
C counter the assumption that we made for this argument. If the clothing are being used more than once by siblings and relatives then the conclusion is shattered that most parents make little use of baby clothing. Hence, C is our answer.