關於英文grammar(e.g +ed/+ing)

以下quotes左果D係答案,亦係我唔明GE答案.

1. 呢題點解要加ing而唔係加ed?
-->The physically "demanding" nature of the jobs does not appear to be a problem for most.

2. tenses ge問題
-->He supported his argument by saying that block grants "are provided" to schools that admit non-Chinese speaking children so that schools mat provide support services to them.
-->點解係are provided而唔係had been provided?
佢by saying that 唔係應該用past tense咩?

3. 又係+ing/+ed ge 問題
-->The Home Affairs Bureau published a report in August 2000, "aiming to" identify the needs of minority groups and the difficulties they faced.
-->點解係aiming而唔係aimed?

其實好多時候我都唔知係+ing/+ed..
anyway, 唔該你>.<!!