關於英文blow off及be covered問題。?

這是 Passive Voice 的問題:
1. .. the blossoms are soon blown off the trees by spring winds (passive voice)
main verb = blow
verb phrase pattern = (subject) blow something (object of verb) off something (object of preposition)

** the sentence in active voice :
spring winds soon blow the blossoms off the tree

It is hence not necessary to use another preposition "from".

2. the ground is covered by a carpet of pink and white petals (passive voice)
main verb = cover
verb phrase pattern 1 = (subject) cover something (object of verb) 覆蓋某物
verb phrase pattern 2 = (subject) cover something (object of verb) with something (object of preposition) 用某物覆蓋某物

*** your sentence has the meaning fit into the pattern 1, so "with" can't be used.
** the sentence in active voice:
a carpet of pink and white petals covers the ground 一層厚厚的粉紅色和白色花瓣 覆蓋 地面

Example using "with"
The workers cover the ground with a layer of tar.
The ground is covered with a layer of tar by the workers. (passive voice)

1. 要是blown away的話,我就會加from. 不然就不加.

2. 應該都可以的.用covered by讓主詞顯得比較被動.用with讓覆蓋的狀況比較均勻.不過還是二者應該都行的.

3. 要問"為神?"應該是個人喜好吧!