In a certain code language, the sentence "it is dark outside" is written as "ha no ti ju", the sentence "is it still raining" is written as "pa ha da no", and the sentence "go and play outside" is written as "su ju ye la". Based on this information, how is the word "dark" written in that code language?

Introduction / Context:
This is a classic word-to-code mapping question. Several sentences are given in English along with their coded forms. Each distinct word is consistently represented by a particular two-letter code. The task is to identify which specific code corresponds to the word "dark".

Given Data / Assumptions:

• "it is dark outside" → "ha no ti ju".
• "is it still raining" → "pa ha da no".
• "go and play outside" → "su ju ye la".
• Each word has one fixed code across all sentences.
• Word order in the code is not important for this question; only the matching of sets matters.

Concept / Approach:
To find the code for a particular word, compare sentences that share some words. Common words will share common codes. Any code appearing only once in a sentence, when all other codes are identified, must belong to the remaining word in that sentence. Here, we exploit overlaps between the given sentences.

Step-by-Step Solution:
Step 1: List words and codes for the first sentence. "it is dark outside" → "ha no ti ju". Words: it, is, dark, outside. Codes: ha, no, ti, ju. Step 2: Compare with the second sentence. "is it still raining" → "pa ha da no". Words: is, it, still, raining. Codes: pa, ha, da, no. Common words in sentence 1 and 2: "is" and "it". Common codes in sentence 1 and 2: "ha" and "no". Therefore, "is" and "it" must correspond to "ha" and "no" in some order. Step 3: Compare sentence 1 and 3. "go and play outside" → "su ju ye la". Common word between sentence 1 and 3 is "outside". Common code between sentence 1 and 3 is "ju". Therefore, "outside" → "ju". Step 4: Now find "dark". Sentence 1 codes: ha, no, ti, ju. We already know: "is" / "it" → ha or no, and "outside" → ju. The only unused code in this sentence is "ti", so "dark" must map to "ti".

Verification / Alternative check:
Check that "ti" does not appear in any other sentence as the code for a shared word. The second and third sentences do not have "ti" at all, which is consistent because they do not contain the word "dark".

Why Other Options Are Wrong:
"ha" and "no" belong to the pair "is" and "it". "su" and "ye" appear in the third sentence, which has no word in common with "dark". Using any of these codes for "dark" would create contradictions in the shared-sentence logic.

Common Pitfalls:
Many learners try to guess based on position or randomly assign codes. The correct approach is to use intersection of word sets and code sets carefully. Always match common words with common codes before assigning the remaining code to the remaining word.

Final Answer:
In that code language, the word "dark" is written as ti.