After ________ absence of 10 years from his hometown, Mr. Li doesn’t know ________ great changes have taken place there.

The number of the foreign tourists to visit the US is expected to be more than 2 million by 20l5, l4 billion to the US economy.[ ]

下列各句中，加点的成语使用最恰当的一句是（ ）

rafting, ___ courage plays an important role, is a breathtaking outdoor sport.

So much of interest ________ that most visitors run out of time before seeing it all.