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Answer:

 solution

Reasoning:

For both given options the number of signals and the expectations ranges for the chemical shifts are identical. The similarities even extend into the fine structure of the signals (two triplets and one singulet if we ignore the aromatic protons for now). However, we can expect significant differences for the chemical shift of the methyl group, depending on whether we deal with molecule a) or b).

Verbindung Equivalent protons d [ppm] (expected) d [ppm] (observed) Multiplicity (expected) Multiplicity (observed)
C6H5-CH2-CH2-O-CO-CH3 -CO-CH3
C6H5-CH2-
-CH2-O-
1.7 ... 2.7
2.4 ... 3.3
3.3 ... 4.6
2.0
2.9
4.3
1
3
3
1
3
3
C6H5-CH2-CH2-CO-O-CH3 -CH2-CO-
C6H5-CH2-
-O-CH3
1.9 ... 3.2
2.4 ... 3.3
3.3 ...4.1
4.3
2.9
2.0
3
3
1
3
3
1

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