Question: What language do they explore?

Evidence:
raw_evidence: The third person plural pronoun `they' has no gender in English and most other languages (unlike the third person singular pronouns `he', `she', and `it'). However Romance languages such as French, Italian, and Spanish, and Semitic languages such as Hebrew and Arabic distinguish between the masculine and the feminine third-person plural pronouns, at least in some grammatical cases. For instance in French, the masculine pronoun is `ils'; the feminine pronoun is `elles'. In all of these cases, the masculine pronoun is standardly used for groups of mixed or unknown gender.
If these sentences are translated into French, then `they' in the first sentence should be translated `elles', as referring to Jane and Susan, and `they' in the second sentence should be translated `ils', as referring to Fred and George.
A couple of examples: The word `sie' in German serves as both the formal second person prounoun (always capitalized), the third person feminine singular, and the third person plural. Therefore, it can be translated into English as either “you”, “she”, “it”, or “they”; and into French as either `vous', `il', `elle', `ils', or `elles'. (The feminine third-person singular German `sie' can be translated as neuter in English and as masculine in French because the three languages do not slice up the worlds into genders in the same way.) Likewise, the possessive pronoun `ihr' in all its declensions can mean either `her' or `their'. In some cases, the disambiguation can be carried out on purely syntactic ground; e.g. if `sie' is the subject of a third-person singular verb, it must mean `she'. However, in many case, the disambiguation requires a deeper level of understanding. Thus, it should be possible to construct German Winograd schemas based on the words `sie' or `ihr' that have to be solved in order to translate them into English. For example,
raw_evidence: What may be more surprising is that currently (July 2016), machine translation programs are unable to choose the feminine plural pronoun even when the only possible antecedent is a group of women. For instance, the sentence “The girls sang a song and they danced” is translated into French as “Les filles ont chanté une chanson et ils ont dansé” by Google Translate (GT), Bing Translate, and Yandex. In fact, I have been unable to construct any sentence in English that is translated into any language using the feminine plural pronun. Note that, since the masculine plural pronoun is used for groups of mixed gender in all these languages, it is almost certainly more common in text than the feminine plural; hence this strategy is reasonable faute de mieux. (It also seems likely that the erroneous use of a feminine plural for a masculine antecedent sounds even more jarring than the reverse.)
The same thing sometimes occurs in translating the feminine plural pronoun between languages that have it. GT translates the French word `elles' into Spanish as `ellos' (the masculine form). Curiously, in the opposite direction, it gets the right answer; the Spanish `ellas' (fem.) is translated into French as `elles'.
The masculine and feminine plural pronouns are distinguished in the Romance languages (French, Spanish, Italian, Portuguese etc.) and in Semitic languages (Arabic, Hebrew, etc.) I have consulted with native speakers and experts in these languages about the degree to which the gender distinction is observed in practice. The experts say that in French, Spanish, Italian, and Portuguese, the distinction is very strictly observed; the use of a masculine pronoun for a feminine antecedent is jarringly wrong to a native or fluent speaker. “Les filles ont chanté une chanson et ils ont dansé” sounds as wrong to a French speaker as “The girl sang a song and he danced” sounds to an English speaker; in both cases, the hearer will interpret the pronoun as referrinig to some other persons or person, who is male. In Hebrew and Arabic, this is much less true; in speech, and even, increasingly, in writing, the masculine pronoun is often used for a feminine antecedent.

Answers:
English, French, German 
French, English, Spanish, Italian, Portuguese, Hebrew, Arabic