Help with intro to Set Theory 
 ^ That's the problem, but I'd also like to know why...
I have:
a. True  
b. True 
c. False, because you'd need to have a set with the null set in it on the right hand side. 
d. True, seems like what was missing from c 
e. True 
f. True 
g. True 
Thanks!

Hint: 


*

*When $a\in A$ then you can find easily $a$ among the other elements of the set $A$.


So, for example $a$ and $b$ are true because you can easily find the element $\emptyset$ in both $\{\emptyset\},\{\emptyset,\{\emptyset\}\}$. While $c$ is wrong, since $\{\emptyset\}$ is not an element of itself. 


*

*When $a\in A$ then we always have $\{a\}\subset A$


So, for example, $f$ is correct. Because in it we see that $\{\emptyset\}\in\{\emptyset,\{\emptyset\}\}$ and so we have $$\{\{\emptyset\}\}\subset\{\emptyset,\{\emptyset\}\}$$
