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 question repeats the same scientific sentence about Mars and again asks you to locate the grammatical error. It checks your ability to recognise an incorrect prepositional phrase that attempts to introduce a reason. Even when the content is scientific, the focus remains on standard English usage, especially when expressing cause and effect.

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 sense is that liquid water cannot exist because the atmospheric pressure is too low.

Concept / Approach:
To express a reason using a noun phrase, English prefers due to or because of rather than as to. The phrase as to commonly means regarding or about and is used to introduce topics, not causes. For example, As to your request means regarding your request. In this sentence, as to low atmospheric pressure is wrong because it tries to carry a causal meaning. The grammatically correct phrasing would be due to low atmospheric pressure or because of low atmospheric pressure. Therefore, the error clearly falls in segment 1.

Step-by-Step Solution:
Step 1: Focus on the part that links the impossibility of liquid water to the explanation involving atmospheric pressure.Step 2: Notice that as to low appears immediately before atmospheric pressure, making the full phrase as to low atmospheric pressure.Step 3: Recognise that as to is not a standard way to express cause, while due to or because of are correct for causal relationships.Step 4: Consider the corrected version: Liquid water cannot exist on the surface of Mars due to low atmospheric pressure.Step 5: Observe that this correction changes only the part contained in segment 1, confirming that this is where the error lies.Step 6: Mark option 1 as the segment with the error.

Verification / Alternative check:
Using the corrected phrase, the full sentence becomes: 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. Each of the remaining segments now fits smoothly. The relative clause in segment 2 gives more detail about how low the pressure is. The exception clause in segment 3 is also grammatically correct. Because only segment 1 required a change, this confirms our choice.

Why Other Options Are Wrong:
Option 2: atmospheric pressure, which is less than 1% of Earth's, is a correct and precise relative clause structure. Option 3: except at the lowest elevations for short periods is a properly formed phrase describing the limited situations in which liquid water might exist. Option 4: No error is incorrect because we have clearly identified a phrase that violates standard expression of cause and would be corrected in good written English.

Common Pitfalls:
Because the sentence contains technical facts and percentages, some students may focus on the scientific information and suspect an error there, but the science is accurate. Others may not be familiar with how as to is used and mistakenly treat it as a generic linking phrase that can mean anything. To avoid these mistakes, remember that each preposition has specific functions. Due to and because of are the usual choices when linking a result with its cause using a noun phrase, while as to is reserved for meaning regarding or in relation to. Recognising these patterns quickly will help you answer similar questions confidently.

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