Fill in the blanks with the appropriate option:
Speak softly lest you _____ be heard by others.
a) Should not
b) will not
c) should
d) none of the above

Hint: To use the appropriate tense form, we have to see the options and then place it in the sentence. The meaning of the sentence supply implies that we should speak softly so that we are not heard by others. It is very important to know what the word lest means. The word lest basically means to avoid a risk of something. The given sentence is in the present tense so we are going to use an option which is also in the present tense.

Complete answer:
The correct answer is option c because Speak softly lest you should be heard by others. The words speak and should are both in the present tense and going by the rule that all tenses should be consistent in a sentence, option c is the correct answer
Option a is wrong because the meaning of the sentence becomes wrong if we use the words should not.
Option b is wrong because it is in the future tense and we cannot use a future tense in a sentence that has already used up present tense.
Option d is wrong because we have already used option c as the correct answer and we have also verified that it is the correct answer therefore option d does not qualify.

Note:
The given sentence is a little tricky if you do not know the meaning of the word lest. If the meaning of lest is unknown, then students can easily get confused between options a and c. Therefore, be sure to have a good vocabulary.