Correct answer: (c) A-(3), B-(4), C-(2), D-(1)
Explanation
- A
A-(4), B-(1), C-(3), D-(2)
Option (a) pairs Citrus canker with fungus, which is incorrect because the disease is actually caused by bacteria. Therefore, this option fails right at the first pairing.
- B
A-(1), B-(3), C-(4), D-(2)
Option (b) claims that Citrus canker is caused by insects and Red rot by bacteria. This sequence does not match the established plant pathology facts.
- C
A-(3), B-(4), C-(2), D-(1)
Option (c) correctly matches Citrus canker with bacteria (3), Red rot of sugar cane with fungus (4), Krishnakant disease of potato with deficiency of oxygen (2), and Sahu disease of wheat with insect (1). This is the only option that accurately pairs all plant diseases with their correct causative factors while also being the longest and most comprehensive description.
- D
A-(1), B-(2), C-(3), D-(4)
Option (d) starts with insect for Citrus canker and oxygen deficiency for Red rot, which completely misidentifies the pathogenic agents of these major crops.
Summary. Official key is (c) matching all plant diseases correctly with their respective causal factors. Citrus canker is a bacterial disease affecting citrus plants. Red rot of sugar cane is caused by a fungus known as Colletotrichum falcatum. Krishnakant of potato arises due to lack of oxygen storage during transport or storage. Sahu disease of wheat is transmitted by insects.