A word series is given with one term missing: Pension, Aptitude, Captain, Tropical, Survive, ?. Choose the correct alternative from the given options that logically completes this series.

Introduction / Context:
This verbal reasoning question presents a series of English words with one term missing and asks you to identify the word that best continues the pattern. The given series is Pension, Aptitude, Captain, Tropical, Survive, followed by a question mark. You must examine the structure of these words to identify a consistent pattern that can be extended to pick the correct option. Pattern recognition in sequences is a common theme in competitive exams.

Given Data / Assumptions:
- Series: Pension, Aptitude, Captain, Tropical, Survive, ? - Options: Parrot, Apply, Trap, Tetrapod and Temple. - All words are meaningful English words. - We assume the series follows some regular structural rule, such as word length or letter arrangement. - We must choose the option that best fits the observed pattern.

Concept / Approach:
One effective approach is to analyze the word lengths and see if a length based pattern appears. Count the letters in each word. Pension has 7 letters, Aptitude has 8 letters, Captain has 7 letters, Tropical has 8 letters and Survive has 7 letters. The pattern alternates between 7 letter and 8 letter words: 7, 8, 7, 8, 7. Therefore, the next word in the series should naturally be an 8 letter word to continue this alternating pattern. Next, we check which of the options is an 8 letter word.

Step-by-Step Solution:
Step 1: Count letters in each series word: Pension (7), Aptitude (8), Captain (7), Tropical (8), Survive (7). Step 2: Observe the pattern 7, 8, 7, 8, 7, indicating alternation between 7 and 8 letters. Step 3: Therefore, the sixth word in the sequence should have 8 letters to maintain the alternation. Step 4: Examine options for word length: Parrot (6 letters), Apply (5 letters), Trap (4 letters), Tetrapod (8 letters), Temple (6 letters). Step 5: Only Tetrapod has 8 letters. Step 6: Hence, Tetrapod is the unique choice that fits the length based pattern and should complete the series.

Verification / Alternative check:
As an additional check, verify that there is no other consistent, stronger pattern using starting or ending letters that would favor a different option. The first letters of the given words are P, A, C, T, S, which do not indicate a clear alphabetic or mnemonic sequence. The last letters also do not form a consistent pattern. Among the options, Tetrapod is the only word that maintains the length alternation in a clear and simple way. Since reasoning with word length is a common device in such questions, this supports our choice.

Why Other Options Are Wrong:
- Parrot has only 6 letters and breaks the 7, 8 alternation rule. - Apply has 5 letters, also violating the established pattern. - Trap has 4 letters, which does not fit any reasonable extension of the sequence. - Temple has 6 letters and again fails to preserve the pattern of alternating 7 and 8 letters. None of these options except Tetrapod matches the length based rule.

Common Pitfalls:
A typical mistake is to search for advanced or obscure semantic connections among the words and overlook simple features like word length. Another pitfall is to attempt to form acronyms or phrases from the words, which is unnecessary here. In many verbal series questions, the simplest observable pattern is the intended one, so always check lengths and basic letter arrangements first.

Final Answer:
The word that logically completes the series is Tetrapod.