In Amoeba, excretion occurs through

The correct option is Plasmalemma.

Let us understand the process of excretion in Amoeba step-by-step:

1. What is Excretion?
Excretion is the process by which metabolic waste products, especially nitrogenous wastes like ammonia, are eliminated from the body of an organism.

2. Excretion in Amoeba:
Amoeba is a unicellular eukaryotic organism. It does not possess specialized complex excretory organs like kidneys. Instead, the primary nitrogenous waste product (ammonia) is soluble in water and is excreted directly through its cell membrane, which is known as the plasmalemma, into the surrounding water by the simple physical process of diffusion.

3. Role of other structures:
- Contractile vacuole: While it does play a minor role in expelling some waste, its primary and major function is osmoregulation (regulating the water balance inside the cell).
- Parapodia: These are locomotory organs found in certain annelids (like Nereis), not in Amoeba (which uses pseudopodia).
- Nucleus: The nucleus is the control center of the cell and regulates genetic material and cellular activities, rather than participating directly in excretion.

Therefore, the major pathway for excretion of metabolic wastes in Amoeba is directly across the plasmalemma.