(a) {{x : x is an even integer}, {x : x is an odd integer}}
(b) {{x : x is an even integer}, {x : x is divisible by 3}}
Note - divisible by 3 includes negative integers, yes? -3, -6, -9, ... and so on?
(c) {{x : x is a negative integer}, {x : x is a positive integer}}
(d) {{x : x is a negative integer }, {0}, {x : x is a positive integer}}
(e) {{x : x is an even integer}, {0}, {x : x is an odd integer}}
From my understanding...
(a) Partition (must be a cover).
(b) Not a cover / partition.
(c) Not a cover / partition.
(d) A partition (must be a cover).
(e) Only a cover.