In the analysis of simple trusses, certain assumptions are made to simplify the calculations and ensure accurate results. Let's examine each statement given in the options and identify which are part of the standard assumptions:

1. All members have the same cross-sectional area. This is not a standard assumption in the analysis of trusses. Members can have different cross-sectional areas depending on the design requirements. Thus, assumption A is incorrect.
2. The bending resistance of all the members is small in comparison with their axial force resistance. This is a valid assumption in truss analysis. Trusses are designed such that the members are predominantly subjected to axial forces — either tension or compression — and bending moments are generally negligible. Hence, assumption B is correct.
3. All the external loads are applied directly or indirectly at the joints. This is a key assumption in truss analysis. It ensures that only axial forces are induced in the members. If loads are applied along the length of the member, it can result in bending, which is not considered in simple truss analysis. Thus, assumption C is correct.
4. All joints are idealized to be frictionless hinges. This is also a standard assumption. The joints in a truss are assumed to act as pins, allowing rotation but not resisting it, thus ensuring members carry only axial forces. Hence, assumption D is correct.

Based on the analysis above, the correct set of assumptions that are standard in the force analysis of simple trusses are:

• B: The bending resistance of all the members is small in comparison to their axial force resistance.
• C: All the external loads are applied directly or indirectly at the joints.
• D: All joints are idealized to be frictionless hinges.

Therefore, the correct answer is:

B, C and D only