english grammar

當然唔係如樓上所講：common sense。如果唔係英文有相當造詣，唔可以用所謂「覺得」、「認為」去估。
我引用 merriam-webster 網上字典（www.m-w.com）o既定義作解釋：
for
1 a—used as a function word to indicate purpose（目的）<a grant for studying medicine> b—used as a function word to indicate an intended goal（目標）<left for home><acted for the best>
呢兩個字義，就正正係 "of great importance for health" o既意思－－運動對健康極重要。
to
7 a—used as a function word (1) to indicate the application of an adjective or a noun <agreeable to everyone><attitude to friends><title to the property>
of great importance to us 應用上，就似上例 attitude to friends，to 就係帶出 importance 係用於其後o既名詞。

it should be for us, no explaination,common sense