Which of the following compound will most easily be attacked by an...

Ortho, para directing groups are electron-donating groups; meta directing groups are electron-withdrawing groups. The halide ions, which are electron-withdrawing but ortho, para directing, are the exception.

Here $- OH$ group is strong electron donating group. Hence electrophile can easily give electron.

$- OH$ group in phenol can release electrons to the ring better than $- C{H}_{3}$ group in toluene. $Cl$ atom has electron withdrawing effect which inhibits electrophile attack readily.