none
Calamansi
This statement is not true. Filipino words can start with various letters of the alphabet, not just the letter "c."
there is no filipino word that starts with letter x unless if you will ask about filipino slang words that starts with letter x.
There is no Filipino word that starts with letter Z. Maybe you can use colloquial words though.
Brahmaputra
Some Filipino describing words that start with the letter "s" are "sariwa" (fresh), "subrang" (excessive), and "malasakit" (compassionate).
Brook
Brain, breast and bronchi are body parts. They begin with the letters BR.
Some examples of Filipino words with diptongos (diphthongs) that include "ey" are "ngayon" (now), "tagumpay" (success), and "br ey t" (bright). These words are formed by combining the vowel sounds of "e" and "y" within the same syllable.
brunt
Xylophone