Several nematodes parasitise a wide variety of plants and animals including ______ . A nematode Meloidegyne incognitia infects the ______ of tobacco plants and causes a great reduction in yield :

Options

A. human beings, stems
B. human beings, flowers
C. insects , roots
D. human beings, roots

Answer

To solve the question, we need to fill in the blanks regarding the nematode Meloidogyne incognita and its effects on tobacco plants.

### Step-by-Step Solution:

1. **Identify the Nematode**: The question mentions the nematode Meloidogyne incognita. This is a well-known plant-parasitic nematode that primarily affects the roots of various plants.

2. **Determine the Hosts**: The first part of the question asks about the variety of plants and animals that nematodes parasitize. Nematodes can infect a wide range of hosts, including humans, animals, and plants.

3. **Focus on the Specific Nematode**: Meloidogyne incognita specifically infects the roots of plants. It is known for causing root knot disease, which leads to significant agricultural losses.

4. **Select the Correct Options**:
- For the first blank, we need to identify a suitable host. Among the options provided, "human beings" is a valid answer since some nematodes can infect humans.
- For the second blank, we need to specify the part of the tobacco plant that Meloidogyne incognita infects. The correct answer is "roots," as this nematode is known to cause damage in the root system of plants.

5. **Final Answer**: Therefore, the completed sentence is: "Several nematodes parasitize a wide variety of plants and animals including **human beings**. A nematode Meloidogyne incognita infects the **roots** of tobacco plants and causes a great reduction in yield."