In this jumbled sentence question, the opening words are “Now the first and most” and the fragments X, Y, and Z must be arranged to complete a sentence about the simple appearance of strata of marine origin above sea level; choose the most logical order.

Introduction / Context:
This question again tests the skill of arranging sentence fragments into a meaningful statement. The content here appears to be from a geology or earth science context, discussing strata of marine origin above the level of the sea in horizontal position. Such passages often appear in reading comprehension or science related questions in exams. The learner must use both knowledge of sentence structure and logical meaning to select the correct order.

Given Data / Assumptions:
The data in the question includes:

• Fixed beginning: Now the first and most.
• Fragment X: strata of marine origin occur above the.
• Fragment Y: simple appearance is where.
• Fragment Z: level of the sea in horizontal position.
• We need the order of X, Y, and Z after the fixed opening.

Concept / Approach:
The intended sentence, when reconstructed, seems to be: Now the first and most simple appearance is where strata of marine origin occur above the level of the sea in horizontal position. This makes both grammatical and scientific sense, describing a simple appearance in geology. The phrase first and most must be followed by an adjective, which is simple. That adjective appears in fragment Y as simple appearance is where, making Y the natural first fragment. Then we need to state what that appearance is, which is where strata of marine origin occur above the level of the sea in horizontal position, combining fragments X and Z in that order.

Step-by-Step Solution:
Step 1: Begin with the fixed part: Now the first and most. Step 2: Identify which fragment can logically follow. Fragment Y begins with simple appearance is where, which fits well: Now the first and most simple appearance is where. Step 3: Next, add fragment X, strata of marine origin occur above the, to state what this appearance is. Step 4: Finally, add fragment Z, level of the sea in horizontal position, to complete the phrase occur above the level of the sea in horizontal position. Step 5: The full sentence becomes: Now the first and most simple appearance is where strata of marine origin occur above the level of the sea in horizontal position. Step 6: This corresponds to the order Y X Z, which matches option b.

Verification / Alternative check:
Check other possible orders. If we tried XZY after the fixed part, we would get Now the first and most strata of marine origin occur above the level of the sea in horizontal position simple appearance is where, which is clearly wrong. Options XYZ or ZYX produce similar confusion in structure and leave the phrase first and most without a proper adjective. Only YXZ provides a smooth flow of subject, linking verb, and descriptive clause, consistent with scientific style.

Why Other Options Are Wrong:
Option a (XZY) puts strata of marine origin directly after first and most, which is grammatically incorrect because first and most needs an adjective such as simple. Option c (XYZ) gives simple appearance is where level of the sea in horizontal position, which is incomplete and wrongly arranged. Option d (ZYX) begins with level of the sea in horizontal position, which does not follow smoothly from first and most and disrupts the meaning. None of these options retain both grammatical correctness and scientific sense.

Common Pitfalls:
Many learners may ignore the phrase first and most and fail to see that it must qualify an adjective. Another pitfall is focusing only on the subject matter, such as sea level and strata, without checking how English clauses normally begin and end. To avoid such errors, always identify where the main verb is, how adjectives are used, and where subordinate clauses start with linking words like where.

Final Answer:
The correct and most logical order of fragments is Y X Z, so the answer is option YXZ.