Adaface Sample Solidity Questions

In the Solidity code provided, there are two contracts: MainContract and HelperContract. MainContract uses delegatecall to execute a function in HelperContract. Carefully analyze the code and determine the outcome of specific operations.

After deploying both contracts and setting the HelperContract address in MainContract, what will be the result of calling setHelperVars(100) from an EOA (Externally Owned Account)?

A: Only HelperContract's state is modified.
            B: Only MainContract's state is modified.
            C: States of both MainContract and HelperContract are modified.
            D: Transaction fails due to the onlyOwner modifier in MainContract.
            E: MainContract's sender and value are modified, but num remains unchanged.
            F: HelperContract's sender and value are modified, but num remains unchanged.

Review the following Solidity code:

We want to add a fallback function to the contract. Pick the correct fallback function and correct statements:

E: Fallback function is executed if contract receives plain Ether without any data
            F: Fallback function is executed if caller calls a function that is not available
            G: If multiple unnamed functions are defined for a contract, the cheapest function is used as fallback function

Review the following Solidity code:

Pick the correct statements:
            
            A: private increment function defined in contract_e is accessible in derived contract d_c but not accessible outside the derived contracts.
            B: private increment function defined in contract_e is accessible only inside contract_e and not accessible to derived contracts as well.
            C: internal variable str defined in contract_e is accessible in derived contract d_b but not outside the derived contracts.
            D: internal variable str defined in contract_e is accessible only inside contract_e and not accessible to derived contracts as well.

You are reviewing a set of two interacting Solidity smart contracts, `ContractA` and `ContractB`. `ContractA` calls a function in `ContractB`, which in turn updates state variables in both contracts. Your task is to determine the correct behavior and gas usage implications based on the pseudo code provided:

The contracts are deployed correctly, and `ContractB` is initialized with the address of `ContractA`. Consider what happens when `incrementBoth` function of `ContractB` is called.

A: Only `ContractB`'s count is incremented; `ContractA`'s count remains unchanged.
            B: Both `ContractA` and `ContractB`'s counts are incremented, with higher gas costs due to inter-contract calls.
            C: Transaction fails due to lack of error handling in `ContractB`.
            D: Gas optimization is achieved due to internal transaction handling.
            E: `ContractA`'s count is incremented twice due to recursive call.
            F: `ContractA`'s count is not incremented due to `external` keyword restriction.