artifact.require() statement in inheritance? - migration

Question

Hi guys my question i very simple.
I have this contract:
B.sol
...
contract A {
...
}
contract B is A {
...
}
When i migrate to blockchain my B.sol i need to deploy every single contracts inside?
Choose one of the answers and explain why please.
var B = artifacts.require("B");
module.exports = function(deployer) {
deployer.deploy(B);
};
var A= artifacts.require("A");
var B= artifacts.require("B");
module.exports = function(deployer) {
deployer.deploy(A);
deployer.deploy(B);
};

Answer 1

The answer you're looking for is most likely #1. When contracts inherit from other contracts, only a single contract is created during deployment. Conceptually, it's the same as other object-oriented languages. From the Solidity docs:
When a contract inherits from multiple contracts, only a single
contract is created on the blockchain, and the code from all the base
contracts is copied into the created contract.
Technically, you can have a child contract that references a deployed parent contract (see below). But, I can't think of a situation where this would be a good design.
pragma solidity ^0.4.18;
contract A {
uint256 public balance;
function() public payable {
balance = msg.value;
}
}
contract B is A {
uint256 i;
A a;
function B(address _a) public {
a = A(_a);
}
function receiveForParent() public payable {
a.transfer(msg.value);
}
function getParentBalance() public constant returns (uint256) {
return a.balance();
}
}
Here, you can deploy A then pass that address in when deploying B. In this case, calling B.balance() or using the fallback function is valid since you're inheriting the logic. However, B.balance() != A.balance(). (Note that B.getParentBalance() == A.balance()).