31. C
32. D
33. B
Explanation:
31. A plant cell is an eukaryotic cell i.e. it contains a membrane-bound nucleus, located CENTRALLY. The nucleus is the largest organelle in the plant cell. The cell/plasma membrane bounds the cell while the chloroplast organelle (site of photosynthesis) is also located in the plant cell. Based on this description, the image in OPTION C is correct.
32. Pottasium (K) is a highly reactive group 1 element. As stated in this question, pottasium reacts vigorously with water (H2O). This reactive property of K element is due to its valence electrons. However, elements in the same group as pottasium i.e same column on the periodic table will have the same number of valence electrons, hence, will behave chemically similar. Therefore, elements in the same column as pottasium will react the same way with water.
33. A reactant is a an element/compound in a chemical reaction that gets used up to form new products. They are usually the starting materials located on the left side of any equation. In this equation shown as:
2CuO + C → 2Cu + CO2
CuO and C are the REACTANTS while Cu and CO2 are the products.
