Solidity automatically generates getter functions for the variables you store, allowing external access to them. When trying to access a specific part of a struct variable like priceFeed from a NetworkConfig type variable, the getter function returns the entire struct, not allowing selective access.

To enable selective access, you can modify the HelperConfig.sol file by adding additional elements to the struct, such as:

  struct NetworkConfig {
      address priceFeed; // ETHUSD price feed
      uint chainId; // chain ID
  }
  ```

When retrieving the struct using `helperConfig.activeNetworkConfig()`, you will receive the entire struct. Subsequently, you can choose which elements to utilize, for example:
 
```solidity
  NetworkConfig memory anvilConfig = NetworkConfig(address(mockPriceFeed), block.chainid);
  return anvilConfig;
  (address ethUsdPriceFeed, uint chainId) = helperConfig.activeNetworkConfig();
  ```

If you only need to store `chainId`, you can discard the `address` part and retain the comma, like so:

 ```solidity
  (, uint chainId) = helperConfig.activeNetworkConfig();
  ```

However, when accessing the struct from within the originating contract, you can directly access its elements without issues:

  ```solidity
  activeNetworkConfig.priceFeed
  activeNetworkConfig.chainId
  ```
This direct access is possible because within the contract, you are interacting with the actual struct, not just a reference to it.