Let's analyze each set of statements and questions:
Question 36:
(1) Fumigants are chemicals that kill or repel pests without affecting stored grains.
Incorrect - While fumigants are meant to target pests, they can potentially affect stored grains.
(2) Water logging decreases the amount of salts in the soil that increases soil fertility.
Incorrect - While water logging can leach salts out, it often negatively affects soil fertility in many cases.
(3) Fertilisers are not readily soluble in water, so they are absorbed by the plants slowly.
Incorrect - Many fertilizers are designed to be soluble and readily available to plants.
(4) Rust of wheat is a fungal disease.
Correct - This is true. Wheat rust is a well-known fungal disease.
(5) The practice of growing two or more dissimilar crops in the same field one after the other is called mixed cropping.
Incorrect - This describes crop rotation; mixed cropping refers to growing two or more crops together at the same time.
So, the only correct statement is (iv).
Option: (C) (i) and (iv) only - is incorrect as only (iv) is true. The correct answer should imply only (iv).
Question 37:
X is the cutting and gathering of crops - this process is known as harvesting.
Y is the separating grains from the crop, known as threshing.
Z is the separation of hay and chaff from the grains by a process called winnowing.
(A) Z is done with the help of wind in which grains along with husk is allowed to fall from a height.
Correct - This describes winnowing accurately.
(B) X is done mechanically by combine and manually by plough and harrow.
Incorrect - While combines are used for harvesting, plough and harrow are primarily for tilling, not harvesting.
(C) X is the process known as threshing whereas Y is the process known as winnowing.
Incorrect - This reverses the definitions; harvesting is X and threshing is Y.
(D) Both (A) and (B) - Since B is incorrect, this option is also incorrect.
Correct answer: (A).
Question 38:
Given the three pots with different organic matter added:
Pot X has green leaves - this could provide some nutrients as they decompose.
Pot Y has old cow dung - rich in nutrients and will enhance plant growth significantly.
Pot Z has urea - provides nitrogen quickly, encouraging growth.
(A) Lot of growth in Z with replenishment of all the nutrients.
Likely correct - Quick growth but not all nutrients are replenished; urea only provides nitrogen.
(B) Lot of growth in X without replenishment of any nutrient.
Incorrect - There may be growth in X but it's likely not as much as in Y or Z.
(C) Lot of growth in Y with replenishment of the nutrients.
Very likely correct - Cow dung is excellent for growth and replenishing nutrients.
(D) Both (A) and (C) - since (A) is only partially true about total replenishment, the choice here is somewhat contested.
Most accurate answer: (C) specifically, but depending on the interpretation of growth and replenishment, (D) could also hold for quick nitrogen growth but lacks full nutrient replenishment.
Final confirmations:
- Question 36 answer: (iv) only is correct.
- Question 37 answer: (A).
- Question 38 answer: (C).