[A] that … should puede usarse después de «it is/was advisable,» «better,» «desirable,» «essential,» «imperative,» «important,» «natural,» «necessary»; después de «fair» (= «just»), «just,» «right» (estos adjetivos a menudo precedidos por «only») y después de «reasonable,» como alternativa a la construcción de for + infintivo:
- It is advisable that everyone should have a map.
- It is better for him to hear it from you.
It is better that he should hear it from you.
- It is essential for him to be prepared for this.
It is essential that he should be prepared for this.
- It is only right that he should have a share.
should a veces se omite delante de be: It is essential that he be prepared.
[B] that … should puede usarse después de «it is/was absurd,» «amazing,» «annoying,» ludicrous,» «odd,» «ridiculous,» «strange,» «surprising,» y adjetivos similares como alternativa a that + presente/pasado:
- It is ridiculous that we should be (= that we are) short of water in a country where it is always raining.
Se usa a veces el infinitivo de perfecto cuando se hace referencia a sucesos pasados:
- It is amazing that she should have said (= that she said) nothing about the murder.
A Practical English Grammar (A.J. Thomson & A.V. Martinet) 