In the following spelling test on English vocabulary, which of the given options shows the correct spelling of the word meaning having skill and competence (skilled or expert)?

Introduction / Context:
Spelling questions in aptitude and language tests assess command over standard English spelling and common word forms. The word here is related to "skill" and describes a person who is competent or expert at something. Many candidates confuse doubled consonants in such words. Recognising the standard accepted spelling is essential for clear written communication and exam accuracy.

Given Data / Assumptions:
- The root word is "skill".
- The meaning required is "having skill" or "showing skill".
- Several options introduce different patterns of doubled letters.
- We must identify the spelling that is widely accepted in standard English usage.

Concept / Approach:
The adjective form of "skill" in standard modern English is "skillful" in American spelling and often "skilful" in British usage, both with a single l in the suffix "-ful". The pattern is to use the full root "skill" and then add the suffix "-ful", but the suffix itself contains only one l. Doubling the l again inside the suffix is not correct. Therefore, the correct form with the given capitalisation is "Skillful".

Step-by-Step Solution:
Step 1: Identify that the question tests the spelling of the adjective meaning "having skill". Step 2: Recall the base word "skill" and the common suffix "-ful", which typically has one l. Step 3: Combine them properly: skill + ful gives "skillful". Step 4: Check option C: "Skillful" matches this combination exactly, with two l's from "skill" and one l from "-ful" forming a single sequence of three l characters in total. Step 5: Compare with other options and confirm that each one has an additional or misplaced consonant.

Verification / Alternative check:
Standard dictionaries and style guides list "skillful" (or "skilful") as the correct adjective, both using only one l in the "-ful" suffix. The pattern matches other adjectives such as "hopeful", "careful", and "useful", where the suffix contributes one l. Options that modify this pattern by doubling letters within the suffix are therefore incorrect. Checking against known correct forms in reference materials supports the choice of "Skillful".

Why Other Options Are Wrong:
- "Skillfull" doubles the l inside the suffix, creating "-full", which is not the standard adjective form.
- "Skillfful" repeats the letter f, which has no justification in the word formation.
- "Skkillful" wrongly doubles the initial k, which is not part of the root spelling of "skill".
Each of these variations violates usual spelling rules for the base word and the suffix.

Common Pitfalls:
A typical mistake is to assume that because the noun "skill" ends with a double l, the suffix "-ful" must also be written with two l's, resulting in an extra letter. Another pitfall is careless copying of letters when writing quickly, especially under exam pressure. Remembering that the suffix "-ful" has one l helps maintain correct spelling for a wide family of adjectives, not just this one word.

Final Answer:
The correctly spelled adjective meaning "having skill" is Skillful.