16. Seven positive integers $a, b, c, d, e, f, g$ are written in a row. Every number differs by one from its neighbours. The total of the seven numbers is 2017 . Which of the numbers can be equal to 286 ?
A only $a$ or $g$
B only $b$ or $f$
C only $c$ or $e$
$\mathrm{D}$ only $d$
E any of them
16. A Each number $a, b, c, d, e, f, g$ differs from its neighbour by one, so they alternate odd and even. To obtain an odd total, we must have an odd number of odd numbers in the list.
Hence $b, d, f$ are odd and cannot be equal to 286 .
If $c=286$, then the biggest total possible is $288+287+286+287+288+289+290=$ 2015 which is too small. By reversing this list, we can also rule out $e=286$.
We can obtain the total 2017 if we start with $a=286$ since $286+287+288+289+$ $290+289+288=2017$. By reversing this, we could also end with $g=286$.