a
When ionic product i.e. the product of the concentration of ions in the solution exceeds the value of solubility product. formation of precitpiate occurs.

\(Ca{F_2} \rightleftharpoons C{a^{2 + }} + 2{F^ - }\)

Ionic product \( = [C{a^{2 - }}]{[{F^ - }]^2}\)

when.  \([C{a^{2 + }}] = 1 \times {10^{ - 2}}\,M\)

\({[{F^ - }]^2} = {(1 \times {10^{ - 3}})^2}\,M\)

\( = 1 \times {10^{ - 6}}\,M\)

\(\therefore \,[C{a^{2 + }}]{[{F^ - }]^2} = (1 \times {10^{ - 2}})(1 \times {10^{ - 6}}) = 1 \times {10^{ - 5}}\)

In this case,

Ionic product \((1 \times {10^{ - 8}}) > \) solubility product \((1.7 \times {10^{ - 10}})\)

\(\therefore \) Hence \((a)\) is correct option.