Multiple choice questions on various topics

If A lab researcher is investigating if gravity affects the distribution of oil and water in the voids of a porous material. Such a material consists of interconnected small tubes $($pores$)$ surrounded by a matrix $($solid$).$ Examples are e$.$g$.$ catalysts, rocks and concrete. The researcher believes that gravity forces $($proportional to $g)$ are competing with capillary forces $($proportional to $).$

The oil he wants to investigate has a density difference compared to water of $=200k\frac{g}{m^3}$ and the oil$-$water interfacial tension is ${}_{ow}=0\mathrm{.}04\frac{N}{m}.$ Unfortunately, he only has some random lab fluid at hand with a density difference compared to water of $=100k\frac{g}{m^3}$ and an interfacial tension of ${}_{fw}=0\mathrm{.}04\frac{N}{m}.$

If the researcher wants to investigate a natural system of length $L=10m$ with a typical $($or characteristic$)$ pore $($capillary$)$ size of $r=5\mathrm{.}0.{10}^{-3}m,$ what typical size should his porous material in the lab have?