The largest and shortest distance of the earth from the sun are $\mathrm{r}_{1}$ and $\mathrm{r}_{2}$ its distance from the sun when it is at the perpendicular to the major axis of the orbit drawn from the sun
(A) $\left[\left(\mathrm{r}_{1}+\mathrm{r}_{2}\right) / 4\right]$
(B) $\left[\left(\mathrm{r}_{1} \mathrm{r}_{2}\right) /\left(\mathrm{r}_{1}+\mathrm{r}_{2}\right)\right]$
(C) $\left[\left(2 r_{1} r_{2}\right) /\left(r_{1}+r_{2}\right)\right]$
(D) $\left[\left(\mathrm{r}_{1}+\mathrm{r}_{2}\right) / 3\right]$