_______ is known to all，China will be an _______ powerful country in 20 or 30 years’ time.
C
as可以用来引导一个非限制性定语从句，通常无明显的先行词。as指代的是主句陈述的内容。而as引导的从句既可以放于句首，也可以放于句末或句中。
The factory _______ we ’ll visit next week is not far from here.
We will ______ you as soon as the new crop comes to the market.
Tourist expenditures have different effects on a destination economy:sales by food vendors to restaurants are _______ effect;while taxi fares and airline ticket sales are _______ effect.
Her mind had been __________ into such a condition as she could not very likely have imagined possible a few months since.
We ___ you for the special offer you send us.( )