Danny's class 1have a party. Danny wants to make a special cake2 the party. He wakes up early in the morning. He won't be 3. Danny begins 4the cake. He puts some flour(面粉), oil(油), milk and a little salt(盐) 5 the bowl(碗). He makes a picture6 it. It 7 like the flag of Canada. But he forgets 8 the sugar. There is 9 in the cake, too. Every piece of the cake 10 a cent in it.

已知$△ABC$中，$c=2b\cos A$，则$△ABC$一定是（   ）

①lmol CH₅⁺中含11N_A个电子

②1mol﹣OH中含10N_A个电子

③lmol C₁₀H₂₂分子中共价键总数为31N_A

④0.4mol以任意比例混合的乙炔和乙醛气体在氧气中充分燃烧时，消耗氧分子数为N_A

⑤1L 1mol/L碳酸钠溶液中含有CO₃^2﹣的个数为N_A

⑥28g乙烯和环丙烷组成的混合气体中含有3N_A个氢原子．