Choose the correct alternative which will improve the part of the sentence given in quotes.
The pedestrians 'should to be' cautious while crossing the road.

Correct option is B

The correct substitution of the quoted words is "should be".
Explanation: The phrase "should to be" is grammatically incorrect due to the inclusion of "to" which is not used with modal verbs like "should." "Should be" is the correct form, indicating advice or recommendation without the infinitive "to."
Grammatical rule used: Modal verbs like "should," "can," and "must" are directly followed by the base verb without "to."
Example: They should be more careful in the future.