The challenge is to write as short a source as possible, where the English alphabet (in alphabetical order from top to bottom) "abcdefghijklmnopqrstuvwxyz" is a subsequence of the source code.

The first mentioning of the next expected letter is the only one that counts. If a letter appears earlier on than expected, then it does not count.

That is: if the letter a is the next expected letter, then in the source b;abs;c; the a counts and everything before it is ignored. The next expected letter in the alphabet is b, which is found immediately as the next letter in abs. That a b existed earlier on in the source has no relevance. Similarly, the s at the end of abs fills no purpose as the next expected letter is now c. And so on, until the whole alphabet has been found in the source.

• Identifiers, variable/function names, string literals, integer/floating point constants (like 0xABCDEF) or anything else that can be named by the programmer do not count towards iterating through the alphabet.
• Only keywords, function names or identifiers provided by the language's standard/default libraries count.
• A solution may use non-standard libraries in which case it becomes a separate "language x + library y" solution.
• Comments are not allowed anywhere in the source.
• The program need not do anything meaningful but must compile cleanly (no language syntax or constraint violations etc) and execute without any crashes or exceptions thrown.
• Function-only answers are accepted and encouraged.
• Any library includes at the top of the program are free and do not count towards the total (if using tio.run, put such in the header section).
• The challenge is case-insensitive, accepting both upper and lower case letters.
• This is code golf, the shortest source that fulfil the requirements wins.

Non-golfed example of a correct solution in standard C:

C (gcc), 217 bytes

void func (void)
{
  fabs;cos;
  #define x long
  acosh;
  printf("hello world");
  jmp_buf j;
  isblank;
  long _Atomic l;
  alignof(int);
  puts;
  qsort;qsort;
  NULL;
  (void)pow;
  fmax;
  INFINITY;
  sizeof j;
}

Try it online!

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To go through this source, func is an identifier and does not contribute to the solution (but to the total amount of characters for code golf like usual). Neither does x, "hello world" etc. We find the alphabet as follows (bold text):

void func (void) { fabs;cos; #define x long acosh; printf("hello world"); jmp_buf j; isblank; long _Atomic l; alignof(int); puts; qsort;qsort; NULL; (void)pow; fmax; INFINITY; sizeof j; }