$.$ Which of the following is used to measure the efficiency of an algorithm? $2\mathrm{.}5$

$[$ A $]$ Number of lines of its pseudo code

$[$ B $]$ The running time of the algorithm on a machine

$[$ C $]$ The number of important operations and space used by the algorithm

$[$ D $]$ The running time of the algorithm on iphone $6$ plus.

$[$ E $]$ The size of the algorithm