To determine the order of amplifiers based on the maximum achievable -3dB frequency, we need to analyze the circuit configurations, particularly focusing on the capacitance affecting the frequency response. The -3dB frequency is inversely related to the effective load capacitance seen by the driver transistor (\(M1\)) that affects the bandwidth. Let's analyze each configuration:

1. Configuration A: This is a single-stage common-source amplifier with a load capacitor \(C_L\). The -3dB frequency is determined by the time constant \(\tau = R_{out} \cdot C_L\), where \(R_{out}\) is the output resistance. This configuration typically has a lower frequency compared to more complex stages due to higher capacitance directly affecting the output.
2. Configuration B: This involves a simple cascode amplifier which increases output resistance, improving bandwidth compared to Configuration A by reducing Miller effect but still affected significantly by \(C_L\).
3. Configuration C: This uses a double cascode configuration, where two cascode stages further increase the output resistance compared to Configuration B. The increased output resistance reduces effective capacitance, thus further improving bandwidth.
4. Configuration D: This is a triple cascode configuration with the highest output resistance and smallest effective capacitance loading, allowing for the highest -3dB frequency. It effectively isolates parasitic capacitances, further enhancing the frequency response.

Understanding these configurations helps infer that the order of amplifiers in ascending order of the -3dB frequency is:

• D: Triple cascode (highest -3dB frequency due to reduced effective capacitance).
• C: Double cascode (moderate improvement over single cascode).
• B: Single cascode (better than single stage but less than double and triple cascode).
• A: Common-source (lowest -3dB frequency due to maximum load capacitance).

Thus, the correct order is: D, C, B, A.