Assertion A is correct. Vertebrates possess a notochord during embryonic development, which is later replaced by a vertebral column.
Reason R is incorrect. All vertebrates are chordates, but not all chordates are vertebrates (e.g., tunicates, cephalochordates). The presence of a notochord at some stage in development is a defining characteristic of chordates. The relationship between chordates and vertebrates is not accurately described in R.

| List - I | List – II | ||
| A. | Lemur | i. | Flying phalanger |
| B. | Bobcat | ii. | Numbat |
| C. | Anteater | iii. | Spotted cuscus |
| D. | Flying squirrels | iv. | Tasmanian tiger cat |
A sphere of radius R is cut from a larger solid sphere of radius 2R as shown in the figure. The ratio of the moment of inertia of the smaller sphere to that of the rest part of the sphere about the Y-axis is : 
A constant voltage of 50 V is maintained between the points A and B of the circuit shown in the figure. The current through the branch CD of the circuit is :
The current passing through the battery in the given circuit, is: 