The industry prevalence, the community size, the installed codebase size, C compatibility, ability to write code at any level of abstraction, etc. makes C++ THE "Industrial Language" to learn.
I keep telling everybody to learn C and C++ irrespective of whatever else they might be forced to study/use since these literally gives them the ability to work at any level in the Software Stack; C is the "universal glue language" and C++ is the all-encompassing monster :-). Bored writing User mode Applications? Jump into writing Libraries/Frameworks/Kernel/Bare-metal code; all using the same familiar language and toolchains. Familiarity trumps everything else. I myself have successfully transitioned from writing Windows desktop apps(16/32-bit) to Network Protocol state machines to Kernel drivers and Bare-metal MCU code all using C/C++.
"Modern C++" (C++11 and later) has shifted the learning goalposts somewhat but nevertheless all the pre-C++11 knowledge is still the bedrock on which to build the new edifices. As a side-note, i completely disagree with people (mainly the "Modern C++" proponents) trying to divorce C++ from its C roots.
Other than C++, the only other language i am willing to spend time on from a professional/industrial pov is Erlang due to its concurrent/distributed/fault-tolerant features.