In the following question, some part of the sentence may have errors. Find out which part of the sentence has an error and select the appropriate option. If a sentence is free from error, select "No error". Liquid water cannot exist on the surface of Mars as to low (1) atmospheric pressure, which is less than 1% of Earth's, (2) except at the lowest elevations for short periods. (3) No error (4)

Introduction / Context:
This error spotting question deals with the correct use of a prepositional phrase explaining a scientific fact about Mars. The sentence explains why liquid water cannot normally exist on the Martian surface. You must identify which part contains an error according to standard grammar rules. The key issue is the incorrect expression as to low, which should be replaced by a correct reason giving phrase.

Given Data / Assumptions:

• Segment 1: Liquid water cannot exist on the surface of Mars as to low.
• Segment 2: atmospheric pressure, which is less than 1% of Earth's,
• Segment 3: except at the lowest elevations for short periods.
• Segment 4: No error.
• The intended meaning is because of low atmospheric pressure.

Concept / Approach:
In English, when we want to express a reason using a noun phrase, we normally use due to, because of, or owing to rather than as to. The phrase as to low atmospheric pressure is incorrect because as to introduces a topic or reference, not a cause. The correct structure here should be due to low atmospheric pressure or because of low atmospheric pressure. Therefore, the error lies in the first segment of the sentence. The rest of the sentence, including the scientific information about pressure and elevations, is grammatically acceptable.

Step-by-Step Solution:
Step 1: Read segment 1 carefully: Liquid water cannot exist on the surface of Mars as to low.Step 2: Recognise that as to is usually followed by a noun or pronoun meaning regarding or concerning, as in As to your question, the answer is complex.Step 3: Note that in this sentence, we need a reason phrase meaning because of low atmospheric pressure.Step 4: Understand that the correct expression would be due to low atmospheric pressure or because of low atmospheric pressure.Step 5: Identify that the error occurs where as to is used instead of due to or because of, which is part of segment 1.Step 6: Conclude that option 1 is the correct answer, indicating the erroneous segment.

Verification / Alternative check:
Rewrite the sentence correctly: Liquid water cannot exist on the surface of Mars due to low atmospheric pressure, which is less than 1% of Earth's, except at the lowest elevations for short periods. In this corrected version, each clause is grammatically sound. Segment 2 correctly uses a relative clause to give more information about atmospheric pressure. Segment 3 properly expresses the exception at the lowest elevations. This confirms that the only real issue is in segment 1, where the wrong preposition phrase is used.

Why Other Options Are Wrong:
Option 2: atmospheric pressure, which is less than 1% of Earth's, is grammatically correct. It correctly uses a relative clause to describe the pressure. Option 3: except at the lowest elevations for short periods is a correct prepositional phrase indicating limited conditions. Option 4: No error cannot be chosen because we have clearly found an incorrect phrase in segment 1, so the sentence is not error free.

Common Pitfalls:
Some learners may be distracted by the scientific content and the use of percentages and think the error lies in the numbers, but those are accurate. Others may not be familiar with the phrase as to and may accept it as correct, especially if they have seen it in other contexts. Remember that as to means regarding or about, whereas due to and because of express cause. In error spotting questions, always focus on the function of the phrase in the sentence. Here, since the phrase clearly introduces a reason, only due to or because of would be acceptable, not as to.

Final Answer:
The error is in part 1; the phrase as to low should be replaced by due to low or because of low atmospheric pressure.