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Hi:

There is a webpage on the Internet saying "For the use of gerund, there is a sentence pattern: It's+adjectives+doing, in which 'doing' is a gerund being used as the subject. like: It's dangerous swimming in the sea in windy days. And the adjectives with the same usage like "It's dangerous doing something with the pattern of "It's + adjectives + doing " are expensive,nice and tiring,etc. " except the words "important and necessary",namely those two words cannot apply to the abovementioned structure. My question is: Is that the case that it is correct to say "It's + all the adjectives except important and necessary+doing something"? Please kindly explain.

In addition, What's the subtle difference in meaning between the following two sentences? Are they both right?

1. It's dangerous to swim in the sea if you cannot swim well (The way I used to like to say more often than the below pattern).

2. It's dangerous swimming in the sea if you cannot swim well .

Thanks a lot!

Xin Yan
Comments 
yanxIs that the case that it is correct to say "It's + all the adjectives except important and necessary+doing something"?

Well, of course, you need to restrict yourself to adjectives that can meaningfully be applied to the thing being done. For example, "It's porous eating noodles" is nonsense. I'm wondering if the relevant question might be this: If the sentence "<doing something> is <adjective>" makes sense, then can we transform it to "It's <adjective> <doing something>"?

As the website says, "It's necessary <doing something>" does seem wrong. "It's important <doing something>" doesn't seem totally impossible in informal speech, but it doesn't seem like perfect English either. There are definitely other examples that don't work, such as "possible" and "forbidden":

"Flying to the Moon is possible." -- OK
"It's possible flying to the Moon." -- No

"Swimming in the lake is forbidden." -- OK
"It's forbidden swimming in the lake." - No

How many more there are I couldn't say.
yanx
In addition, What's the subtle difference in meaning between the following two sentences? Are they both right?

1. It's dangerous to swim in the sea if you cannot swim well (The way I used to like to say more often than the below pattern).

2. It's dangerous swimming in the sea if you cannot swim well .

I don't discern any difference in meaning. Stylistically I prefer the first.