In determing viscosity (eta) by poiseuille's method the formula used eta = (pi p r^(4))/(8 vl). Which of the quantities in the formula must be measured more accurately

In determing viscosity (eta) by poiseuille's method the formula used e

1.	In determing viscosity (eta) by poiseuille's method the formula used eta = (pi p r^(4))/(8 vl). Which of the quantities in the formula must be measured more accurately
Answer» p r v l Answer :B