Word puzzle: fill the double blanks in _ _ s _ _ de with the same pair of letters to make a valid English word.

Introduction / Context:
This puzzle asks us to complete an English word that has two identical missing letter pairs. The pattern is written as double blanks, followed by s, another two blanks, and then de: _ _ s _ _ de. The same two letters must go into both pairs of blanks to form a real word. Word completion puzzles of this kind encourage careful attention to spelling structure, repeated patterns, and vocabulary knowledge.

Given Data / Assumptions:

• The target is a single English word with seven letters.
• The pattern is AB s AB de, where AB is the same two letter sequence both times.
• The completed word must be a standard dictionary word.
• We must choose from the given options which word fits this pattern.
• No extra letters can be added or removed; only the blanks are filled.

Concept / Approach:
We translate the pattern into a letter structure: positions 1 and 2 are some letters A and B, position 3 is s, positions 4 and 5 are again A and B, and positions 6 and 7 are d and e. So the word is AB S AB D E. We then check each candidate word to see if positions 1 2 and 4 5 contain the same pair of letters and whether the rest of the pattern matches sde at the end. The first option that satisfies both conditions and is a valid word is the answer.

Step-by-Step Solution:
Take cascade: spelling is c a s c a d e. Positions 1 2 are c a, position 3 is s, positions 4 5 are c a, and 6 7 are d e. Thus cascade fits the structure AB S AB D E with AB equal to c a. Verify that cascade is a standard English word meaning a waterfall or series of small waterfalls. Now briefly inspect other options for the same repeated pair structure.

Verification / Alternative check:
Passcode is p a s s c o d e, which does not match the pattern because it has eight letters and the ending is code rather than de. Lowside is l o w s i d e, where the repeated pair condition is not satisfied: positions 1 2 and 4 5 are l o and s i, which are different. Miscode is m i s c o d e, also not of the form AB S AB D E. Only cascade respects the exact structure with a repeated two letter pair before and after the s while ending in de. Therefore cascade is the unique correct answer.

Why Other Options Are Wrong:
Passcode breaks the length and ending pattern. Lowside and miscode have different letters in positions 1 2 and 4 5, so there is no repeated pair AB as required by the puzzle. These incorrect options are plausible looking words designed to test whether the solver is carefully checking the full pattern rather than just glancing at the overall shape of the word.

Common Pitfalls:
A typical mistake is to ignore the requirement that the same pair of letters must fill both blanks, leading solvers to accept any word that vaguely fits _ _ s _ _ de. Another issue is not counting letters carefully and choosing words of the wrong length. To handle similar puzzles, it is helpful to write down the index positions and verify letter by letter that every condition is satisfied. This rigorous check is especially important in multi option verbal reasoning questions.

Final Answer:
The completed word is cascade, obtained by filling both blanks with the pair c a.