A protection method applied to electrical equipment that does not produce arcs or sparks in normal service and under specified abnormal conditions, in which additional measures are applied so as to give increased security against the possibility of excessive temperatures and of the occurrence of arcs and sparks, is type of protection $?$

a$.$ flameproof $"$d$"$

b$.$ increased safety $"$e$"$

$q,$ c$.$ intrinsic safety $"i"$

$q,$ d$.$ none of the above