Out of the four alternatives given, choose the one which can be substituted for the words Hard working and diligent.

Introduction / Context:
This one word substitution question tests the learner knowledge of subtle differences between words that look similar but have very different meanings. The phrase Hard working and diligent describes a positive quality that is valued in academic and professional settings. Recognising the precise adjective that expresses this idea is useful vocabulary for both examinations and real life use.

Given Data / Assumptions:

• Description: Hard working and diligent.• Options: Seditious, Sedate, Sedulous, Scheming.• The correct word must express steady, careful hard work.• We assume standard dictionary meanings of these adjectives.

Concept / Approach:
Sedulous is an adjective that means showing dedication and diligence, or working very hard and carefully. The other words, though similar in spelling, mean completely different things. Seditious refers to encouraging rebellion against authority. Sedate means calm and unhurried. Scheming implies making secret plans, often dishonest ones. Only sedulous captures the sense of hard working and diligent.

Step-by-Step Solution:
Step 1: Identify the key qualities in the description steady hard work and careful attention.Step 2: Recall that sedulous is used in phrases such as sedulous student and sedulous research, indicating persistent hard work.Step 3: Examine seditious, which is linked to sedition and means causing people to rebel against the state.Step 4: Consider sedate, which describes calm, quiet behaviour, not necessarily involving hard work.Step 5: Look at scheming, which implies plotting or planning, often with a negative or dishonest intention.Step 6: Conclude that sedulous is the only word that fits the given description.

Verification / Alternative check:
Try using each option in a sentence where hard working and diligent would fit naturally. She is a sedulous employee immediately conveys the idea that she works conscientiously and with effort. She is a seditious employee would suggest that she encourages rebellion in the workplace. She is a sedate employee merely indicates that she is calm. She is a scheming employee highlights dishonesty or plotting. Only sedulous preserves the positive sense of diligent work.

Why Other Options Are Wrong:
Seditious has a political and negative meaning and does not describe work habits at all. Sedate focuses on quiet and calm behaviour and may even suggest a lack of energy. Scheming indicates making secret and often selfish plans, which can be clever but is usually not a compliment. None of these words express the steady, positive effort and care signalled by the phrase hard working and diligent.

Common Pitfalls:
The main difficulty here is visual similarity. Candidates may confuse sedulous with seditious or sedate because of the shared starting letters. The best way to avoid this is to learn such words in example sentences that show their emotional tone and typical context. Remembering sedulous student as a phrase that praises effort can help anchor the correct meaning in memory.

Final Answer:
The one word substitute for Hard working and diligent is Sedulous.