$3.[2$ pts$]$ Which triaxial tests can be used to determine the undrained shear strength of clays?

$($a$)$ Consolidated$-$drained & Consolidated$-$undrained

$($b$)$ Consolidated$-$undrained & Unconsolidated$-$undrained

$($c$)$ Consolidated$-$drained & Unconsolidated$-$undrained

$($d$)$ Consolidated$-$drained & Vane shear

$4.[2$ pts$]$ Suppose we ran three undrained triaxial tests in the laboratory on saturated clay specimens, and we used confining pressures of $100$ kPa, $200$ kPa, and $300$ kPa for the three tests, respectively. If we plotted the Mohr$$s circles at failure, what would be the value of the undrained friction angle determined from these three tests?

$($a$)0$; $($b$)45\backslash$deg ; $($c$)60\backslash$deg ; $($d$)$ cannot be decided.

Please answer $3$ and $4.$