Correct : b,c

To determine which sequences of events can never happen, we must analyze the logical dependencies between the Translation Lookaside Buffer (TLB), the Page Table, and the Cache memory.
1. Analyzing TLB and Page Table interaction
The TLB is a fast hardware cache specifically for the Page Table. If a memory reference results in a TLB hit, the physical address is obtained immediately, and the main memory Page Table is bypassed entirely. Furthermore, the TLB only stores translations for pages that are currently present in the main memory. Therefore, if there is a TLB hit, it is impossible to have a "Page table miss" (page fault). They are mutually exclusive. This makes Option B impossible.
2. Analyzing Page Table Miss and Cache interaction
A Page table miss (or page fault) occurs when the requested page is not currently present in the main memory (RAM) and resides on the secondary storage (disk). The problem explicitly states: "when a page is evicted from the main memory, the corresponding blocks in the cache are marked as invalid." Because cache is a subset of main memory, if a page is not in the main memory, its data absolutely cannot be valid in the cache. Therefore, a Page table miss dictates that there must be a Cache miss. A sequence with a Page table miss followed by a Cache hit is impossible. This makes Option C impossible.
3. Evaluating Valid Options
Option A: TLB miss (translation is not cached), Page table hit (page is found in RAM), Cache hit (data happens to be in cache). This is a completely normal and valid sequence.
Option D: TLB miss, Page table miss (page fault, fetch from disk), Cache miss. This is the standard sequence when accessing a completely unmapped or newly requested page. This is valid.
Correct Answers: B, C ✓