Which of the following pairs of numbers has HCF 14 and LCM 210?

Write the numbers as $14a$ and $14b$ with a, $b$ co-prime; then LCM = $14ab=210$ gives $ab=15$, so (a, b) = (3, 5) or (1, 15). The pair 42 and 70 fits: HCF = 14, LCM = 210, and $42\times 70=2940=14\times 210$. Watch the near-misses - 42 and 105 have the right LCM (210) but HCF 21, while 56 and 70 have the right HCF (14) but LCM 280; 28 and 105 give HCF 7 and LCM 420.