Explanation

I: 107 ≡ −15 and 76 ≡ 15 (mod 61), so 107^100 − 76^100 ≡ (−15)^100 − 15^100 = 0 (mod 61) since 100 is even — correct. II: 67^5+33^5 is divisible by 67+33 = 100 for odd exponent 5 — correct. Both hold — option C.