App closure settings


Hi guys
Im very sorry if this is a massively obvious thing but this is my first foray into smartphones so bare with me.
I was playing around with the setting and can across a button which gave me the option of making the phone close apps when I exited them, however since selecting this my phone has slowed down considerably when moving around the desktop section.
I am now trying to undo this setting change and cannot for the life of me work out where i changed it.
Hope this sounds familiar to someone.
Thanks in advance for any help

p.s. the phone is a HTC desire C


of the cuff the only way i can quickly think, is in Developer Options (within Settings)
scroll down to section Apps
and untick Don't keep activities

Hope this helps