Question

It ___ (rain) since four hours. therefore, they ___ (wait) at the bus -stop as they have no numbrellas with them. (fill in the blancks with proper forms of the verb's given in brackets)​

Answer 1

The blanks in the sentences should be filled as shown and explained below:

It has been raining for four hours. Therefore, they are waiting at the bus -stop as they have no umbrellas with them.

Explanation

We use the present perfect continuous for an action over a period of time leading up to specific time. We also use 'for' and 'since' with the stated time period or duration.  

The verb form for this tense is:

has/have+been+V1+-ing

Present Continuous tense is used to talk about actions that are currently going on in the present moment.

Its verb form is: : S+is/am/are+V1+-ing+O

Answer 2

it has been raining since 4 hours

they are waiting at the bus stop as they have no umbrellas with them