1.
a. No problem.
b. Aliasing problem.
c. No problem.
d. Aliasing problem.
e. No problem.

2. 
a ---->10
       ^ ^
c -----| |
d -------|

b ----> [1, 2, 3, 4, 5]

3. 
def apply_every_other(l, f):
    result = []
    
    for i in range(len(l)):
        if i % 2 == 0:
            result.append(f(l[i]))
            
    return result


4. 
DFS: No.  It will depend on how the state space is searched.  If we're not careful, DFS could get stuck searching s -> a -> s -> a ...

BFS: Yes.  Even though BFS will also explores s -> a -> s -> a ... it will also explore other paths at the same time and will eventually find the solution.