Question

with a little effort we_____keep our surroundings clean (should/can).​

Answer 1

With a little effort, we can keep our surrounding clean.

Answer 2

With a little effort we can keep our surrounding clean.

• There are two options in the question - 1) Should , 2) Can
• Now, "should" is used in a sentence whenever we need to convey (or, to give advice) that something is the appropriate thing to do.
• On the other hand, "can" is used in a sentence whenever we need to convey ability or possibility.
• Now, in the given sentence a possibility of keeping surroundings clean, is conveyed, if we are able to give little effort about it. Due to this "possibility" indication, we've used "can" in the given sentence.