The correct statement about Agni-I is that it is a single stage, solid fuel missile.

Option 1 highlights that the Agni-I missile is propelled using solid fuel and does not have multiple stages. This means that it does not undergo any separation or staging during its flight. A single stage missile is simpler in design and easier to operate compared to multi-stage missiles.

Option 2, which states that Agni-I has a maximum striking range of 1000 kms, is not correct. The Agni-I missile actually has a range of around 700-800 kms, which is less than 1000 kms.

Option 3, stating that Agni-I is a double stage missile, is incorrect. As mentioned earlier, Agni-I is a single stage missile.

Option 4, which claims that Agni-I has a maximum striking range of 1500 kms, is also incorrect. The correct range of Agni-I is within 700-800 kms, falling short of 1500 kms.

In summary, the correct statement is that Agni-I is a single stage, solid fuel missile with a range of around 700-800 kms.