To answer this question, let's go through each option to understand why it is correct or incorrect:
Option A) Worm - This option is incorrect because a worm is a type of malware that spreads copies of itself to other computers without any human intervention. It does not specifically target anti-virus programs.
Option B) Retrovirus - This option is correct. A retrovirus is a type of computer virus that actively attacks an anti-virus program or programs to prevent detection. It tries to disable or bypass the anti-virus software to remain undetected.
Option C) Trojan - This option is incorrect. A Trojan is a type of malware that disguises itself as a legitimate program to deceive users. It does not specifically target anti-virus programs.
Option D) Ghost virus - This option is incorrect. There is no specific type of virus called a "Ghost virus."
The correct answer is B) Retrovirus. This option is correct because it describes a computer virus that actively attacks an anti-virus program or programs in an effort to prevent detection.