Hazards

Structural Hazard

LW    F   D   B0  B1  W
LW    F   D   (D) B0  B1  W

As both the instructions are simultaneously asking for the load pipeline, a structural hazard is observed. This is resolved by stalling till the pipeline is freed.

Data Hazard

ADDIU R5, R6, 1    F   D   B0  B1  W
ADDIU R7, R5, 1    F   D   (D  D   D) A0  A1  W

The second instruction depends on the first. So stalling is done until the value of R5 is resolved.