From the given alternative words, select the single word which cannot be formed using the letters of the word PHOTOSYNTHETIC. Each letter from the base word may be used only as many times as it appears there.

Introduction / Context:
This word formation question uses the base word PHOTOSYNTHETIC. You are asked to choose the option that cannot be formed from its letters. This kind of question trains you to quickly detect missing letters and to be aware of how often each letter appears.

Given Data / Assumptions:

• Base word: PHOTOSYNTHETIC.
• Options: THOSE, SCENT, PRONE, COTTON, STONE.
• No new letter that is not present in PHOTOSYNTHETIC may be used.
• No letter can be used more times than it appears in the base word.
• Standard English spelling is assumed for all words.

Concept / Approach:
The systematic approach is:

• Write down all letters of PHOTOSYNTHETIC and count their frequencies.
• For each option, verify that each letter appears in the base word.
• Ensure that the required count for each letter does not exceed the available count.
• If an option uses a missing letter or overuses some letter, it cannot be formed.

Step-by-Step Solution:
Step 1: List letters in PHOTOSYNTHETIC: P, H, O, T, O, S, Y, N, T, H, E, T, I, C. Step 2: Count them: P = 1, H = 2, O = 2, T = 3, S = 1, Y = 1, N = 1, E = 1, I = 1, C = 1. Step 3: Check THOSE. It needs T, H, O, S, E. The base word has T, H, O, S, and E with sufficient counts, so THOSE can be formed. Step 4: Check SCENT. It needs S, C, E, N, T. All these letters occur in PHOTOSYNTHETIC at least once, and T is abundant, so SCENT can be formed. Step 5: Check COTTON. It needs C, O, T, T, O, N. Required counts are C = 1, O = 2, T = 2, N = 1. The base word has C = 1, O = 2, T = 3, N = 1, so COTTON can be formed. Step 6: Check STONE. It needs S, T, O, N, E. The base word has S = 1, T = 3, O = 2, N = 1, E = 1, so STONE can be formed as well. Step 7: Check PRONE. It needs P, R, O, N, E. Letter R is required, but R does not appear anywhere in PHOTOSYNTHETIC. Because R is missing from the base word, PRONE cannot be formed.

Verification / Alternative check:
A quick method is to scan each option for any letter that is absent in the base word. All letters in THOSE, SCENT, COTTON, and STONE can be found within PHOTOSYNTHETIC. However, R appears in PRONE but not in the base word. This immediately shows that PRONE cannot be constructed, without needing detailed counts of the other letters.

Why Other Options Are Wrong:
THOSE uses only letters already present in PHOTOSYNTHETIC and does not overuse any of them. SCENT uses S, C, E, N, and T, all of which are available with sufficient counts. COTTON uses C, O, T, and N in numbers that the base word can easily supply. STONE uses S, T, O, N, and E, again all present within the available frequencies.

Common Pitfalls:
Examinees often focus on longer or more complex words like COTTON and assume they must be impossible. Others forget to verify a single missing letter like R. Training yourself to quickly scan the base word for each letter in the option, especially consonants, can significantly reduce errors in such problems.

Final Answer:
The word that cannot be formed from PHOTOSYNTHETIC is PRONE, because the letter R is not present in the base word.