我正在尝试在考试 R 包中构建一个真假问题。这是一个单选练习，答案列表中只有两个可能的答案。这是代码：
Question
========
¿Puede una variable clasificarse como cualitativa continua?
Answerlist
----------
* Si
* No
Solution
========
No es posible ya que una variable continua debe ser nesezariamente una variable cuantitativa.
Answerlist
----------
* False
* True
Meta-information
================
exname: Escalas de medicion 01
extype: schoice
exsolution: 01
exshuffle: 2
运行exams2html(question.Rmd)输出后有三个可能的答案，包括NA
我做错了什么？
会话信息：
> sessionInfo()
R version 4.0.2 (2020-06-22)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Ubuntu 18.04.4 LTS
Matrix products: default
BLAS: /usr/lib/x86_64-linux-gnu/blas/libblas.so.3.7.1
LAPACK: /usr/lib/x86_64-linux-gnu/lapack/liblapack.so.3.7.1
locale:
[1] LC_CTYPE=en_US.UTF-8 LC_NUMERIC=C
[3] LC_TIME=es_CO.UTF-8 LC_COLLATE=en_US.UTF-8
[5] LC_MONETARY=es_CO.UTF-8 LC_MESSAGES=en_US.UTF-8
[7] LC_PAPER=es_CO.UTF-8 LC_NAME=C
[9] LC_ADDRESS=C LC_TELEPHONE=C
[11] LC_MEASUREMENT=es_CO.UTF-8 LC_IDENTIFICATION=C
attached base packages:
[1] stats graphics grDevices utils datasets methods base
other attached packages:
[1] forcats_0.5.0 stringr_1.4.0 dplyr_1.0.0 purrr_0.3.4
[5] readr_1.3.1 tidyr_1.1.0 tibble_3.0.3 ggplot2_3.3.2
[9] tidyverse_1.3.0 exams_2.3-6 pacman_0.5.1
loaded via a namespace (and not attached):
[1] Rcpp_1.0.5 cellranger_1.1.0 pillar_1.4.6 compiler_4.0.2
[5] dbplyr_1.4.4 tools_4.0.2 jsonlite_1.7.0 lubridate_1.7.9
[9] lifecycle_0.2.0 gtable_0.3.0 pkgconfig_2.0.3 rlang_0.4.7
[13] reprex_0.3.0 cli_2.0.2 rstudioapi_0.11 DBI_1.1.0
[17] haven_2.3.1 withr_2.2.0 xml2_1.3.2 httr_1.4.2
[21] fs_1.4.2 generics_0.0.2 vctrs_0.3.2 hms_0.5.3
[25] grid_4.0.2 tidyselect_1.1.0 glue_1.4.1 R6_2.4.1
[29] fansi_0.4.1 readxl_1.3.1 modelr_0.1.8 blob_1.2.1
[33] magrittr_1.5 backports_1.1.8 scales_1.1.1 ellipsis_0.3.1
[37] rvest_0.3.5 assertthat_0.2.1 colorspace_1.4-1 stringi_1.4.6
[41] munsell_0.5.0 broom_0.7.0 crayon_1.3.4