Discussion

Explanation:

x = 16³ + 17³ + 18³ + 19³

= (16³ + 19³) + (17³ + 18³)

= (16 + 19)(16² − 16 × 19 + 19²) + (17 + 18)(17² − 17 × 18 + 18²)

 35 × (an odd number) + 35 × (another odd number) = 35 × (an even number) 

= 35 × (2k) … (k is a positive integer)

∴ x = 70k

∴ x is divisible by 70.

Remainder when x is divided by 70 = 0

Hence, option (a).

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