Identify the true statements regarding hiigh-throughput fracture toughness tests using indentation.

a) Can only obtain quantifiable fracture toughness values when the material is relatively brittle.

b) Spherical indenters are used.

c) If material has high toughness, greater than 15 MPa m^(1/2), then it will not be possible to determine the local variations in fracture toughness.

d) Uses a minimal among of material to establish a fracture toughness value compared to a convenient fracture toughness test.

e) It is possible to investigate how fracture toughness varies spatially across a sample.