How can you explain the statement "Implicitrequirements can also be unknown unknowns"?$2-$There are matters that should be$,$ but are not, elicited through the elicitation process. They exist, but they are not realized. This includes issues such as security requirements$\mathrm{.}3-$An unknown unknown cannot be known and therefore we can not make them explicit requirements$\mathrm{.}4-$During the SRS process, customers should always be required to spell out their unknown unknowns.