Select the most appropriate option to fill in blank no. 5.
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e. has been witnessed.
“Has been witnessed” = present perfect passive.
Subject: “A … increase in cyberattacks” (singular).
Correct verb form: “has been witnessed”.
Meaning: We have observed (and are still observing) an increase in such cyberattacks.