单选题：It' s the first question parents ask when their child is dia

It' s the first question parents ask when their child is diagnosed with autism ( 自闭症). Will his future brothers or sisters have a higher risk of46it, too?
According to the largest study of siblings (兄弟姐妹)in families with autism, the answer is yes. Among 664 children who had at least one older sibling with the developmental disorder, the47risk of autism was nearly 19%,48higher than previous sibling recurrence estimates that were anywhere from 3% to 10%. Kids with more than one older autistic sibling hadan even higher risk of the disorder:32%.
The 49suggest that genes play a key role in autism risk. But they also hint that other environmental factors50 by siblings, like influences in the womb (子宫), many be important as well.
On the51 of the findings, the researchers recommend that doctors closely52younger siblings of autistic children to pick up any early signs of the disorder,53an unusually large head or delayed language development and communication skills. Evidence suggests that early54 and diagnosis of autism can help children take advantage of therapies that can treat some of its55
根据以上内容，回答题．
第46题答案是 ______ A．average
B．basis
C．common
D．consequently
E．detection
F．developing
G．distributed
H．dramatically
I．including
J．monitor
K．reason
L．results
M．shared
N．symbols
O．symptoms