CEH v13 details that fragmentation attacks are a common IDS evasion strategy. Signature-based IDS systems depend on reassembling packets to detect malicious patterns. When attackers fragment TCP headers into smaller segments, the IDS may be unable to reconstruct the original packet sequence, especially if the fragments are intentionally crafted to confuse reassembly buffers. Meanwhile, the target host typically recombines the fragments correctly, allowing the scan or payload to pass undetected. This technique is specifically discussed under IDS evasion methods, where fragmentation prevents complete packet inspection. Options A and B describe unrelated evasion mechanisms such as IP spoofing and MAC spoofing, and Option C does not fundamentally affect IDS reconstruction. The tester is clearly using packet fragmentation to evade detection while still mapping open ports successfully.