Understanding the concept of "מצוה" in S'char shabbos.
If One Says Words Without an Action Attached to It: Are Words One Speaks הכנה?;
is one allowed to pull a thread to tighten a hem, cuff, button, etc. on Shabbos;
(Melting ice.) understanding the difference between "מוליד" and "נולד"; leaving out frozen items on a counter;