Q: If I stumbled., can we say that "I hit my knee hard when I hit the ground."?

A: it is not possible to tell

Q: If (And the high concentration of oxygen in the atmosphere that sustains life on this planet--hey, it's on me!), can we say that "(Hey, it's on me--the high concentration of oxygen in the atmosphere that sustains life on this planet.)"?

A: yes

Q: If A surer recipe for disaster has never been devised., can we say that "This is as sound a strategy as can be found."?

A: no

Q: If And then I shouldn't be so damned hard up as I am now.", can we say that "I shouldn't be so hard. "?

A:
yes