In the letter pattern _ yzaa _ y _ xy _ aazy _, which one set of letters, when placed in the blanks from left to right, will correctly complete the series?

Introduction / Context:
This question involves a partially hidden sequence using the letters x, y, z, and a. The pattern is written as _ yzaa _ y _ xy _ aazy _, and you must choose a five letter set to fill the blanks from left to right. Many such alphabet test questions are built by repeating a fixed block of letters. Here, finding that underlying block is the key to solving the problem.

Given Data / Assumptions:

• Skeleton pattern: _ y z a a _ y _ x y _ a a z y _.
• There are five blanks to be filled in order.
• Answer choices: xxzzx, xxaza, xzxzx, aazzx, zzxax.
• The completed series should form a simple, repeating block pattern with no contradictions.

Concept / Approach:
The letters y, z, a, and x appear repeatedly, hinting at a short block such as xyzaa or xyzaazyx. A useful technique is to try an option and then see whether the resulting full string can be split into equal sized repeating segments. The correct option should produce a string where a fixed block of letters repeats exactly, which is typical in exam style series completion problems.

Step-by-Step Solution:
Step 1: Represent the blanks as x1, x2, x3, x4, x5 and write the pattern as x1 y z a a x2 y x3 x y x4 a a z y x5. Step 2: Test option C, xzxzx, which assigns x1 x, x2 z, x3 x, x4 z, x5 x. Step 3: Substitute these values. The completed string becomes: x y z a a z y x x y z a a z y x. Step 4: Now group the sequence into two equal blocks of 8 letters each: first block x y z a a z y x, second block x y z a a z y x. Step 5: Both blocks are identical, so the full series is simply the block xyzaazyx repeated twice. This is a very clean and regular pattern.

Verification / Alternative check:
Check briefly that other options do not create the same kind of neat repetition. For instance, using xxzzx produces the string x y z a a x y z x y z a a z y x, which cannot be split into identical halves or into a simple repeating block of reasonable length. Option B xxaza gives uneven blocks where one part is xyzaa but the other part does not match. Options D and E also lead to irregular strings where no short block repeats exactly. Thus, only xzxzx gives the repeating pattern xyzaazyx xyzaazyx.

Why Other Options Are Wrong:
With xxzzx, repeated letters occur in places that break the symmetry between the first and second half of the sequence. xxaza gives a partial occurrence of xyzaa, but the rest of the letters do not align to form identical blocks. aazzx and zzxax introduce combinations like aa or zz in positions that destroy the neat xyzaazyx structure. Therefore these combinations cannot be the intended completion of the pattern.

Common Pitfalls:
A common pitfall is to try to match only the beginning of the sequence and stop once the first few letters look promising. Another mistake is to search for a complicated rule relating positions and letters, when the actual pattern is just a repeated block. Writing out the full string for each candidate option and checking whether it splits into equal, identical segments is the most reliable technique for such problems.

Final Answer:
The set of letters that correctly completes the series is xzxzx, giving the repeated block xyzaazyx twice.