6.
如图,正方体
\(ABCD\)\(-\)
\(A\)\({\,\!}_{1}\)
\(B\)\({\,\!}_{1}\)
\(C\)\({\,\!}_{1}\)
\(D\)\({\,\!}_{1}\)中,
\(M\),
\(N\),
\(Q\) 分别是棱
\(D\)\({\,\!}_{1}\)
\(C\)\({\,\!}_{1}\),
\(A\)\({\,\!}_{1}\)
\(D\)\({\,\!}_{1}\),
\(BC\)的中点\(.\)点
\(P\)在对角线
\(BD\)\({\,\!}_{1}\)上,且\(BP= \dfrac{2}{3}B{D}_{1} \),给出下列四个命题:
\(①\)\(MN\)\(/\!/\)平面\(APC\);\(②\)\(C\)\({\,\!}_{1}\)\(Q\)\(/\!/\)平面\(APC\);\(③\)\(A\),\(P\),\(M\)三点共线;\(④\)平面\(MNQ\)\(/\!/\)平面\(APC\)\(.\)其中正确命题的序号为_________
![](https://www.ebk.net.cn/tikuimages/2/2018/500/shoutiniao29/d5c279afafb62d6cfde6cf9bb1e5abe0.png)