Misc: In 1921 Mongolia gains independence from ---------- (National Day). ?

Questions

In 1877 The opera "---------- et Dalila" is produced (Rouen). ?

In 1901 ---------- patents 1st disposable razor. ?

In 1915 Randolph ---------- newspaper publisher, born. ?

In 1942 1st controlled ---------- chain reaction (University of Chicago). ?

In 1958 Benelux treaty signed by Belgium, ---------- & Luxembourg. ?