The occurrence which most likely would have no effect on 2020 net income (assuming that all amounts involved are material) is the

worthlessness determined in 2020 of stock purchased on a speculative basis in 2016.

sale in 2020 of an office building contributed by a stockholder in 1989.

collection in 2020 of a receivable from a customer whose account was written off in 2019 by a charge to the allowance account.

settlement based on litigation in 2020 of previously unrecognized damages from a serious accident that occurred in 2018.