[A]: Lateral-iine organs are important in con- nection with aquatic mode of life.
[R]: They are highly supplied with branches of cranial nerves and they are entirely disap- peared in terrestrial forms.

Options

A. If both A and R are true and R is the correct explanation of A
B. If both A and R are true but R is not the correct explanation of A
C. If A is true and R is false
D. If both A and R are false

Answer

### Step-by-Step Text Solution:

1. **Understanding the Question**: The question presents two statements:
- Statement [A]: Lateral-line organs are important in connection with aquatic mode of life.
- Statement [R]: They are highly supplied with branches of cranial nerves and they are entirely disappeared in terrestrial forms.

2. **Analyzing Statement [A]**:
- The lateral-line organs are indeed crucial for aquatic animals, particularly fish. They serve as sensory organs that help these animals detect changes in water pressure and movement, which is essential for navigation, hunting, and avoiding predators.

3. **Analyzing Statement [R]**:
- The statement claims that lateral-line organs are highly supplied with branches of cranial nerves. This is true as these organs are innervated by cranial nerves, allowing them to function effectively.
- However, the latter part of the statement claims that these organs are entirely absent in terrestrial forms. This is misleading. While lateral-line systems are less developed or absent in many terrestrial animals, some amphibians retain them during their aquatic life stages.

4. **Conclusion**:
- Therefore, Statement [A] is true as lateral-line organs are important for aquatic life.
- Statement [R] is partially true but misleading because while they are less prominent or absent in many terrestrial forms, they are not entirely absent in all. Thus, we can conclude that [A] is true and [R] is false.

### Final Answer:
- Statement [A] is true.
- Statement [R] is false.

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