The intended meaning of the sentence is that 'over 6M hectares of emerald bamboo groves flourish in China', these groves are one-fifth of the world's reserves. They also spread from the saturated border of Yangtze to the borders of the Nanling Mountains in the southern part of the country.

Option A - Incorrect
The phrase 'spreading from' in the sentence could either be modifying China or the groves. Even if it is modifying 'China,' it is an error in intending meaning that the groves flourish because they spread from 'Nangling to the southern part.'

Option B - Incorrect
This changes the intended meaning of the sentence. The sentence says that over 6M hectares of emerald bamboo is 1/5th of the world's reserves, but this option says 1/5th of the world's 6M reserves.

Option C - Incorrect
This option has the same issue has option B. It evens restricts it to only bamboo groves that spread. This also changes the intended passage meaning.

Option D - Correct
Here, 1/5th refers to the hectares spreading from Nangling and 'flourish' correctly modifies the 6M hectares of emerald bamboo grooves.

Option E - Incorrect
Again, '1/5th of the world's reserves of emerald bamboo groves' changes the intended meaning. This option also claims that the bamboo groves flourish and spread which is opposite to the intended meaning.