The singular form of were is was:
I was at the beach.
Jane was at the beach.
We were at the beach.
All of us were at the beach.
The exception is the singular you still uses were, it doesn't distinguish between the singular or plural of you:
When were you at the beach?
The singular form of the demonstrative pronoun 'these' is this.
The singular form of "that" is "it."
"Stratum" is the singular form of stratum. The plural form is "strata".
A singular form of dice is a die
The singular form of Oases is, Oasis.
The singular form of the demonstrative pronoun 'these' is this.
The singular form of "that" is "it."
it is already in its singular form.
The singular form is cuff.
"Stratum" is the singular form of stratum. The plural form is "strata".
The form hypothesis is the singular form. The plural form is hypotheses.
A singular form of dice is a die
The singular form of feet is foot.
The singular form of Oases is, Oasis.
The singular form of chromosomes is a chromatid.
"Wash" is the singular form of "wash."
The singular form of diagnoses is diagnosis.