$1.$ If the data in cache is updated, it needs to be written back to the main memory using write$-$through or $2.$ This bit called bit telis you whether you need to write back to the main memory $3.$ In a $2$ way associative array with a total of $16$ blocks, the picture could be drawn with how many rows and columns. rows by coluns $4.$ If the data a program is looking for is not there in main memory, where will the OS start looking for it$?$