What isotope and element can be used to determine if skeletal remains are recent or ancient?

A) 210-lead
B) 210-polonium
C) 210-bismuth
D) There currently is none that can do this.

Draw a mechanism that shows how the product is formed.

Given that compound X has a molecular formula of C₆H₁₀O₂, gave three peaks in its ¹³C NMR spectrum (14, 63 and 158 ppm) and two peaks in its ¹H NMR spectrum (1.4, triplet and 4.3 ppm, quartet), provide a structure for compound X.