Step 1: Understanding the Concept:
Different nutrient deficiencies have specific symptoms.
We need to identify the correct statements.
Step 2: Key Formula or Approach:
No specific formula.
Need to know nutrient deficiency symptoms.
Step 3: Detailed Explanation:
A. Magnesium deficiency: chlorosis between veins (interveinal), veins remain green.
This is correct.
B. Iron deficiency: interveinal chlorosis appears on young leaves, not older leaves.
So, B is incorrect.
C. Manganese deficiency: brownish black spots in pea and grey speck of oat.
This is correct.
D. Boron deficiency: brownish/reddish young leaves, shoot and root death.
This is correct.
Thus, A, C, and D are correct.
Step 4: Final Answer:
The correct statements are A, C, and D.
Hence, the correct option is (C).